All Wheel Drive Auto: Independent Seattle Subaru Service


Subaru Air Conditioning Explained

Typical Subaru Air Conditioning Problems Explained.

The Air conditioning (AC) system in your Subaru is made up of the following.

A compressor, Condenser, Evaporative (Evap) core, Expansion valve, receiver dryer, hoses and lines, thermo sensor and the controls.  Inside the car there are a series of ducting or blend doors and their respective controls.  I am not really going to give a class on how the ac system works I will save that for another article.

Anytime you notice a situation where the Ac system isn’t blowing cold air, there is some sort of a problem with the ac system.  Driving down the road at 60 mph brings in a rush of air that may feel cool to you, just like standing in front of a box fan in your house provides some temperature decrease.  But if the ac doesn’t actually feel cold there is a problem.

When the ac system is in fact not performing as it should a diagnosis must be performed.  When an ac system has a low charge, the performance will most definitely suffer.   But it’s also possible to have a ac system that has a full charge and not blow cold as well.  The possibilities are many and in some circumstances the problem may be hard to diagnose or have more than one issue.

Adding to this is that it is normal to lose about 2 ounces of R134a out of an automotive system every year with no real leaks.  So, on the one hand the system could just be low enough to not function correctly after 4 years with no real problems or it can be low as a result of a leak.

I wanted to point out some of the current issues we see.

The 2000 to 2004 Legacy and Outback suffer from leaks at the 2 Ac hoses one from the compressor to the condenser and one form the compressor to the Evap core.  This causes the system to run low or empty.  It’s a very correctable situation and if not fixed properly will just cause the R134a gas to leak back out causing the problem you were trying to fix to reoccur.  To find the leak test equipment is needed.

2002 to 2003 Subaru Impreza, (all models and trim levels) has an issue where the Evap core can ice over as a result of a design issue to the system, Subaru has issued a service bulletin about it.  The fix is a new thermosensor (which is located in the Evap core).  This requires taking the Evap core out of the vehicle which is partially removing the dash components on the passenger side.  I usually suggest replacing the expansion valve at the same time.

The 2001 to 2004 Outback with the H6 has some of the same leaky hose issues that plague the 4cylinder models.

The newer Ac systems (2005 and up) are smaller than they have been previously and even just a slightly low charge can affect the performance.

Typically speaking we only think about the Ac system when it isn’t working correctly, but the reality is, it really should be serviced at least every 4 years.   As the system loses some of the refrigerant as part of what is considered normal, it is replaced with air, which creates moisture in the system, which periodically needs to be removed through a process called evacuation, which involves hooking up a vacuum pump and putting the system into vacuum, the system should than be re-oiled and recharged with refrigerant and this good maintenance can help ensure your ac system will work when you want it to.

Thanks for reading



490 Responses

  1. Hi Justin,
    We have a 2010 Forester. A couple years ago the A/1c cycled between blowing cold and warm air. We took it to a repair shop and he said it was overcharged (however that happens), but he fixed it.
    About a month ago the A/C started acting up; it will blow cold for 10-20 min maybe, then starts blowing warm. We finally took it to the same repair shop. We were told the condensed had s pin hole and it was replaced. This did not fix the problem. We took it back in the compressor was replaced and maybe valves and other things. Basically we have a brand ne A/C unit and this has not solved the problem. We took the car back to the shop, they adjusted the factory setting to shut off at 80 to 49, this still did not fix the problem.
    I am not mechanically minded, don’t know much about cars, but it seems to me that the problem is somewhere between the A/C and the vents.
    Any insight is greatly appreciated. The car will be going back, we’ve paid enough they are going to have to fix it.

    1. Hi Brenda,

      Sounds frustrating. This statement right here has me scratching my head “they adjusted the factory setting to shut off at 80 to 49, this still did not fix the problem” If that’s actually what they said they did you have just got to find another shop as its gibberish.

      I wish I could help you but I need gauge readings, Scan tool data and temperatures to begin to diagnose an AC issue.

      Sorry I cant offer more.


      1. Thanks, I knew it was a long shot. Unfortuneately we can’t affor to put more money into it and they are going to have to fix ix it. The last thing they told us was that it is probably another system pulling the cool air, I don’t know if I have that right, but . . .

  2. Hello,

    Is my 2011 Subaru Legacy 2.5i supposed to have an A/C relay? My fuse box in the engine compartments shows a spot for it but no actual relay installed. When I looked up the part at AutoZone, it did not even give the option of an A/C relay so I’m wondering if it maybe my car isn’t suppose to have one.

    1. Hello Noelle,

      The only way you do not have an Ac replay is if you do not have AC. No idea why Autozone does not show an Ac relay. Anyways you are correct that there is no relay in the under hood fuse block in the 2011+ despite showing one there. It was moved to I believe the relay block behind the Glove box panel if memory serves.


  3. Hi Justin,

    In your opening paragraph, you say “ I am not really going to give a class on how the ac system works I will save that for another article.”

    Have you written that article? I really would like to know all the details on the system. I think it is more complex than one might assume. Inquiring minds want to know.

    Thank you!!!
    JK Smith

    1. Hey JK,

      No there just is not enough time to dive into that for me right now. Owning two shops and just having a family keeps me as busy as I can handle at times.

      There are a lot of AC system information out there already. The only thing I really bring to the table is Subaru Speak.


      1. Justin,

        2003 Forester XT here. AC cabin outlet normally runs at around 60Deg with temp setting at 75Deg. However, lately it occasionally drops down to 40Deg at which time it turns off. Looking under the hood the low pressure line is iced-up. Also, on several occasions, a large cloud of fog smelling like freon has poured out of the hood. Any advice on what’s wrong and how to fix it?

        Paul in San Diego

        1. Hey Paul,

          Sorry, but not without looking at it.

          To many “could be” to list. Guage readings are the next step.


  4. hi i have a 2014 outback, i had the ac serviced about a year ago, but recently my ac started acting funky, it will run but not very cold unless its on max, and if i am driving around town at regular speeds i start getting warm air, then it cools down again if i am going over 60, or freeway speeds ? coolant is good and no lights or noises present, could it be as simple as the cabin air filter or more likely the compressor ?
    any ideas would be great ?

    1. Hey Roy,

      That really just needs to be looked at locally. Most likely its got a low charge with some sort of leak repair needed, but an engine running hotter that normal, or a Condenser that is experiencing restricted airflow and other items as well could also be the cause. The first step s to install a set of Ac gauges and look at the pressure readings.

      Hope that helps.


      1. Hello Justin. I have a 2016 Subie Forester with 76k. Bought new to me in 2018. Since July 2020 it has been plagued with a/c issues and under warranty at dealership had replaced the compressor, condenser, 1 O ring, and relay switch “for good measure” and it is STILL not cold, smells humid/moist, and does not leak condensation. I have another appt with the dealership but what else can it be?

        1. Hello Michelle,

          Sounds awful, I wish there was something I can offer, but it just needs to be properly diagnosed. The list of what could be wrong is just to long to contemplate. Pressure readings, scanning the computer to see if it thinks the Ac is on or off request and if it thinks its on or off when it is. What needs to be known is do we have a Ac control problem, or a system failure somewhere. We could still have a low charge but we could also have a system not capable of turning on do to some sort of malfunction with a control or request.

          Someone can figure it out, you just have to find that someone.


  5. Justin, My 2009 Outback A/C seems to work fine but since it is 12 years old could I add some 134A refrigerant to the system and expect cooler air on real hot days, or maybe just not worry about it? The dealer cleaned the cabin air filter last time I was there and reported no leaks in the system.

    1. Hey Phillp,

      It would be better to have a preventative service somewhere VS just adding blind. If you have the R134a recovered, than drawn down into a vacuum for 15-30 minutes, filled with the proper amount of pag oil and fresh R134a, that would be a much better way to go. The moisture in the system is the real killer to the Ac components.

      Thanks for the Question


  6. Justin I just have to say I been reading over the entire blogs and as a somewhat pro tech this had me rolling all over the floor. Its a shame that advance auto or auto zone or any of the other places for that sake don’t explain that just cause a DTC or some sort of ecu code pops up that those are just only used for the emissions side of things to keep the car in check from polluting and that just cause it says …. code sensor one dead or yada yada that just replacing the part isn’t always going to fix the original cause of why that code came about in the first place. If all these DIYs want to really do it right get some sort of real time info scan tool yes they cost thousands and every car manufacturer has one for its own makes and models but pay the 5-15,000.00 bucks and then learn how to use it and wow look what this thing shows me DATA DATA DATA lol and OMG its live too! lmao. IJust can’t imagine you doing a somewhat normal day at the shop then replying to all theses questions which is why us technicians went to school or learned it through experience the hard way yeah. People just want it now asap now now now lol you have to understand each entire system of your vehicle and once you understand how it works then cha ching that light will go off but man props to you and yes you need to open a garage for subies over here on the east coast seriously man. Take care and have a wonderful forth and stay health and safe.

  7. Hi Justin,

    I have a 2007 Subaru outback and for the first time in 8 years I changed the cabin air filter. I run a lot of dirt roads around here in Montana and it was 99-100% clogged. I changed it and may have noticed a fuel efficiency increase. I know the cabin air filter really has nothing to do with the engine, except with the A/C on, which can put a load on the alternator and cause the fuel injectors to throw more fuel and air when needed. I am really curious if you know what happens when the A/C is on the coldest temp fan is on and there is no extra air flow going into the evaporator? Will this cause the expansion valve to work harder causing more load on the a/c compressor or is all of this irrelevant and wouldn’t change mpg?

    Thank you,

    1. Hey Erik,

      Actually that is a great question. The answer is yes, overtime any deficiency no matter how small will affect the AC system performance, which will increase the “on time” of the system, which will affect fuel economy as the load form the compressor is actually still pretty significant on a 2007 model.

      One thing of note is this will really show up as a miles per tank thing over time, not so much a miles per gallon equation, which is really the only thing most divers notice.

      In Montana be on the every year replacement going forward.

      Thanks for posting!


  8. I have a 2013 2ltr diesel outback. When I accelerate hard I get and noise coming from the aircon even though its off. The noise starts around 1700 rpm. Sounds like the fan is engaging but not sure as there does not seem to be any airflow from vents. Does not happen when in park and you accelerate to bring rpm above 1700 rpm. Also is not consistent.

  9. Justin,
    I greatly appreciate you taking time to reply as I know how busy you are, operating a sizeable repair shop. First off, I should have stated in my initial message that I drove those two vehicles just to get a very general “feel” for each model. The 2020 is more than I want to spend.

    Anyhow, below are bullet points synthesizing what I’ve gleaned from 6 replies to my posts on the Subaru Outback owners and Edmunds forums. I rarely am on such message boards but am I right to assume that most replies will occur within a few days after the initial posting? If you have time, I’d welcome any disagreements, endorsements, amplification, etc. that you might have. If not, I understand completely.

    All things being equal, Outbacks are slightly more expensive than Foresters. Forester has a more SUV upright type of driving position than Outback. Right now, I drive a RAV4 but also am the original owner of a 50 year-old Cutlass, so either position is OK. Thanks to keeping the Cutlass and hand-me-downs from in-laws, I’m definitely a novice car shopper, as I’m sure is obvious.

    Forester is slightly better off road but both models can likely handle “fairly mellow terrain” (one poster’s lingo) equally well. Barring a move or vacation to the mountains and off-roading there (unlikely), that probably describes where I’ll be driving. Due to very long overhangs, the Outback loves to catch its bumper shells on things. For regular off-roading, get tires with robust sidewalls (e.g., not the tires that are normally put on these cars). I may need to investigate potential spare storage problems (I take it that Subaru does not allow enough storage space for an inflated, full-size spare).

    CVTs got a little better after 2016. One poster: “For towing either 2.5L or 3.6L will do. I am not a fan of the CVT with the 3.6L.” I don’t anticipate towing but guess I can’t rule it out.

    One poster gave lots of info, re: oil consumption problems history of Foresters. Nevertheless, he said his favorite Forester is the SH, MY 2011-13, IF the short-block replacement has been done. He suggested reading up on the class-action suit about those engines (not how I envisioned car shopping but maybe I should). One poster’s 2011 Forester 2.5i Premium (67K miles) uses about 1/2 qt. of oil @ 6,000 miles and his Outback 2017 2.5i Limited (45K miles) rarely uses any between changes.

    Finally, only one post addressed my A/C concern. Even though I don’t anticipate having lots of back seat passengers, that could change and I want to be sure that the vehicle can cool adequately, especially in a climate where daily temperatures can range from lows in the mid-70s to highs of 100+ for three to four months each year. Actually, when I’m alone, 90 degrees is often my threshold temperature for turning on A/C.

    In light of the above, I’d say that I’m leaning towards a 2016-19 Outback with less than 80,000 miles, spending $20,000 max. My filters for searches have included single owner, no accidents, and service documentation, in addition to price and mileage. Of course, that screens out a lot right there. I know that there’s a tradeoff between mileage and price so I may need to give in on at least one of my preferences. Again, I am grateful to you for replying to my initial query and for any additional thoughts that you might have.
    Thanks very much,

  10. Justin,
    I just located your site. I’m trying to decide between purchasing a Forester or an Outback. I’ll keep it for at least 3-4 years and put about 7,000 miles/year on it. About 1/4 of those miles will be driving around cattle pastures and the vehicle will be parked outside (unfortunately). So, I’m looking for a used vehicle (2014-2017 models), nothing fancy. I’ve driven a 2010 Forester (Carmax) and a 2020 Outback (local dealer) and like them both. While I can’t tell a lot of difference between them, aside from the Outback’s slightly lower seat, one consideration here in Texas is good A/C for the entire car. Edmunds and Subaru forums have some posts indicating that Outback may be superior in that regard. Anyhow, if you don’t advise prospective buyers along these lines, I apologize for bothering you. I just thought that your opinion would be valuable as an expert without “a dog in the fight.” Thanks very much.

    1. Hey Sam,

      Pretty different cars you have described there.

      Fuel economy is going to be better in the 2020 but at 7000 miles a year the savings is negligible. 2010 Forester is a great car, and its issues all well known so less potential surprises, the 2020 is under warranty however.

      My advice is that they both will do the exact same thing, its a tool. They are both good quality tools, why pay more for one tool over another to do the same job?

      Id have a pre purchase inspection done on the Forester and if it checks out really give the savings some thought.


  11. Hi I have a 2001 llbean outback with the H6. My a/c blows hot the compressor is running, the high side hose gets hot like it should and the low side hose is warm not getting cold and sweating. Is there something that could be plunged? Like a orifice tube of some sort ?

    Thanks Don.

  12. Hey Justin,

    Wow can’t believe this throat has been going on for 2011. Thank you for helping all these strangers that have reached out to you. The world really needs more people like you!

    I am in need of some advice as well!
    I have a 2004 Subaru Forrester which I picked up with only 65,000 miles the car was was stored for a long time withMinimal use.

    When I got it the AC was not Blowing cold air but I figured it must have leaked out the refrigerant so I filled it at a/c shop and had cold air for about a month. The mechanic told me it was most likely the evaporator without even looking at it and quoted me upwards of $500 for replacement. I I was weary and could not afford this at the time so I just refilled it. Then it lasted for about a year after which my compressor clutch got jammed. Did some research online and ended up getting a good deal on the new compressor, so I went to another shop replaced compressor along with the condenser, expansion valve, and did system flush. Turns out the high-pressure hose was leaking and was noticeable upon inspection just by lifting the foam pad that covers it. I went ahead and replace that hose as well.

    The air technician at the shop told me that the evaporator was most likely leaking as well. He tried looking with a camera and said it looked like it needed replacing but couldn’t identify any obvious leaks.

    My questions:
    In your experience, should I just go ahead and replace the evaporator as well for optimal performance?
    …will this improve cooling even if no leaks?

    or… Should I just wait and see if my A/c starts acting up again prior to changing the evaporator? I already have the parts, But the labor itself cost more than the parts. 

    Is it likely that the culprit of all the problems with my A/c was the high pressure hose leak and not the evaporator?

    Thanks in advance!!

    1. Hello Ricardo,

      Sorry for the Delay in responding but I took a few days off. The common issue on your era Forester is the high and sometimes low side hose and O-Rings leaking. We just dont see a lot of Evap Cores leak. Id run it as is and enjoy the cool air.

      Hope that helps


  13. Hi Justin….

    Have an 01 Subaru Forester that the a/c works sometimes, blows cold then warm. Notic d that when running the car accelerating and slowing to stop some weird loud noise comes from the unit. Popped the hood one time to look at it, and the black piece on the front of the compressor would stop spinning causing the ac to stop. Have tighten the belt hoping that would work but it did not. Any advice as to what could possibly be the problem? Hope I have given enough details to get a response. Thank you in advance. It’s hot in N.C.!

    1. Hi Sandy,

      That is just a situation that is going to need to be addressed. The black thing that stops spinning is the Compressor Clutch and it cycles on and off normally, if it doesn’t blow cold, it could have a low charge or something else going on. First place to start is gauge readings.


  14. I got an automatic 2006 Forester with 145K. A/C will blow real cold for about 5-10 minutes, then the compressor will shut off and not kick on again unkess I turn off the A/C for about 10-15 minutes. When I turn it back on, the problem repeats (5ish minutes of cold air then the compressor shuts off again). Pressure is fine in the lines, but I put a little more AC Pro in just to be sure, and unfortunately it didn’t do anything. Tried to check the expansion valve to see if it was frosting or icing over, but I couldn’t see anything (I think the valve is behind the firewall in this model. I followed the lines into the wall but couldn’t see the valve or any ice/heavy frost on the lines). Any ideas?

    1. Hello Alex,

      Ive said this 100 times on this site

      You cant diagnose an Ac issue on a Modern Car without scan data and gauge readings. Its just not possible.

      When it stops working what is the high side pressure, and what is the low side pressure, when you shut the car off do they equalize? When the Ac kicks of does the Computer still show ac request and does it show it commanded on or off. If commanded on where is the signal loss, Switch, Relay? If commanded off why, what input into the ECM has put ac function into cancel. Those are the answers you need

      Adding R134a to a system at capacity will also not do anything but harm the system.

      If your going to guess throw a relay at it


      1. I don’t have any scan data unfortunately, so it sounds like I’ll just need to to take it in and have it looked at. As much as I love guessing, I’ll probably just make it worse. Thanks for the help!

        1. Hey Alex,

          Without Scan data and gauge readings your missing key information in order to be able to properly diagnose, it would be better to have it diagnosed.

          Hope it all works out before summer is over


  15. hi Justin, I just have a quick ?, my wifes 2014 impreza is having a/c issues, her freon is good, but when you first start the car the air is ice cold but after driving for awhile it the ice cold goes away and is just cool air and sometimes it goes back to ice cold again but of i stop and shut car off for a few minutes it will be ice cold again when I turn back on, the blower motor resistor needs replaced but not sure if that is problem, any advice or input would be appreciated!!!!

  16. 2005 outback, a/c charged good, 12v good, no ecm command at a/c relay. dash switch seems to work (led on/off) but ecm show switch off at all times. I see a “through j/c” on wiring diagrams but cant find it. thoughts?

    1. Hello Jayme,

      I would check input/output of the Switch and then at the ECM. maybe there is a bad pin.

      I have seen that before


  17. Hi!

    I’ve got a 2014 Subaru Forester XT Touring with 75k. It’s previous home was Florida (I’m sure the AC saw some use). The AC seems to work well, but the output seems to fluctuate in a regular pattern, from ice cold to moderate/neutral cold. The fan is consistent, it’s just the temperature of the output that seems to fluctuate. Could this be the EVAP sensor or the charge. As the recent second owner, I’m not sure the last time this AC system was serviced… Thanks for considering.

    1. Hey Danny,

      That sounds like a slightly low charge, ac needs to be serviced every 2 years or so on average in order to maintain peak performance.

      I would start there.

      Hope that helps.


  18. Hi Justin I have read this entire post. You are truly talented with Subaru’s. I have an 04 outback. 2.5l. Today I replaced the cabin air filter behind the glove box. AC worked on way home from getting the filter. I changed the filters and put it all back together and now the compressor won’t engage. What is the electrical sensor on the filter door? If i damaged that item or broke a wire could that affect the compressor operation? Thanks in advance for any information / advice
    Rich P.

    1. Hey Rich,

      Yes if that temp sensor @ the Evap core is damaged it wont allow proper function.



  19. Hi,

    I’ve been reading all these terrific comments re Subaru air conditioning, but I haven’t found my issue.
    I have a 2009 Subaru Forester.
    My issue is that I have no heating on the driver’s side (Australian vehicle, so right hand drive). On the passenger’s side I get hot and cold air from all the vents and the system works as expected. On the driver’s side, I only get cold air. The centre console, the windscreen and the side window vent all have no heating, regardless of the temperature or air direction setting.
    I have looked at the various controls under the dash (using a small camera) and I can see things change when I move the temperature control, and things move when I change the air direction switch (foot, face, screen etc.)
    I had my local dealer perform a ‘diagnosis’ and they said it was a heater core issue that would involve removing the dashboard to access the part. LOTS of money and many hours of labour.

    Any thoughts?


  20. Hi Justin,

    As a mechanic my field of expertise is old GM vehicles. Man is the AC simple on those. A low pressure switch and a high pressure switch with no complicated expansion valve to go bad. Just a restrictor filter combination.

    Now I’ve got a new to me 2009 Forester XT and am trying to learn Subaru’s thinking on AC systems. These are pretty complicated compared to the stuff I’m used to. Of course all the sensors run into the computer that has the last say on whether to run or not and it could possibly be bad. I really like the car other than the persistent low idle RPM.
    One day* noticed AC wasn’t working well and really seemed intermittent. Threw the gauges on it and it acted like it was a bit low on refrigerant but the cutoff was really random. Sometimes the clutch would just stutter. As the low pressure dropped it might cut out at 18psi or 25psi or 30psi. Sometimes it would cut in and run for just 1 second or maybe two seconds.
    Now correct me if I’m wrong but instead of switches like the old GM stuff had this car uses sensors and the computer does the switching through a relay(which seems good since swapping it out made no difference).
    Does this car have a low pressure sensor that has just gone bananas? I suspect there are a couple issues going on here and it’t the possible electrical one that is going to be the problem. I also suspect that the previous shops may have over charged with oil. I suspect the dryer may be full of oil but I’m not even sure where the dryer is. I say that because capacity is somewhere near 14? oz but a 12 oz can over fills it. We are talking low pressure of near 60to80 and high pressure over 300. 3/4 of a 12 oz can seems to bring the pressures in range but its very pressure sensitive.
    Now I am aware that low working gas volume due to an oil overcharge would make it very pressure sensitive but don’t think it can account for all the craziness.
    Originally I thought the thermal expansion valve was bad simply because even when the compressor was running steady the pressure variations on the low side were crazy. In fact I have worked on many AC systems and never seen one where at idle the pressure on the low side would jump around so fast and so much. Also the high side was running really high and I think actually exceeded 400 psi with the low side still too low (18psi)(possible slight over charge at the time)
    Not finding a lot of information online about that system. Do you know what kind of a sensor setup it uses and where those sensors are?

    1. Hello Bryan,

      Gm uses a Accumulator/Orifice tube based ac system where its controlled mostly by the ECM monitoring low side pressure, when its low its switched off. Generally this is called the low pressure cycle switch.

      Most Japanese car makers use the Receiver dryer/expansion valve type system, that doesn’t monitor low side values. Typically speaking there is generally a revolution sensor, high side cut out switch but nothing like the GM system.

      Id be looking at the AC relay and or the clutch to Coil values VS spec.

      Hope that helps


  21. I have a 2002 Subaru Impreza Outback Sport. I recently recharged the AC and it was working great. Now within the last week the passenger side 2 vents still blow ice cold. But the driver side ones are are hardly blowing cold air. I assume that some vent might be stuck open. But I am not sure and not sure how to even find that vent or issue. Do you have any ideas? Thank you.

    1. Hi Tom,

      That’s something you just need to either dive into yourself or pay a professional to do. There are numerous possibilities. I also don’t from here know if its an airflow issue or a temp issue?
      Was not clear in your post if your feeling warm air instead of cold or low air flow.


  22. “As the system loses some of the refrigerant as part of what is considered normal, it is replaced with air, which creates moisture in the system, which periodically needs to be removed”

    You sir need a class on fundamentals refrigeration & physics.

    A pressurized system (above atmosphere) cannot be replaced with air.

    1. Okay Don,

      If you have a leak in the low side of an “Automotive Ac System” on a Subaru, the Ac compressor can still engage and in some instances actually try to pull the system into what’s called “Vacuum” if it’s low enough. Perhaps you have heard of Vacuum? It’s what happens in the absence of pressure.

      The more the system leaks out, the more air can potentially be pulled into the system.

      Since you clearly have a “PHD” (I hope you see Mike Meyers as Dr Evil when you read that) I know I sure do…

      Let me ask YOU a few questions.

      What is the pressure of the low side of a Subaru’s AC system when running, VS atmospheric pressure?

      What happens to that value as the system becomes low on refrigerant? Does it go up or does it go down?

      Is atmospheric pressure a constant across the world or does it vary?

      Is Ac making something cold, or taking the heat out?

      Have you heard of the term “suction line” ?

      Do you know the total capacity of a modern Subaru’s Ac system?

      Did you know that it’s less than it was a decade ago?

      Does Subaru utilize a low pressure cut off switch or do they rely on high side pressure to turn off and on the Ac compressor?

      I guess that is a good start

      But Hey Don’t take my word for it

      So I googled the term “how does Air enter an Ac system”

      There was 277,000,000 links to click on, I copied the very first one for you, clearly he’s an idiot as well.

      In closing, I am not sure what you think gives you the right to post something like you have, but in all honesty you really need to take a hard look in the mirror man, and ask yourself how that makes the world a better place.


  23. Hi Justin,
    I have a 2012 outback. Dealer has diagnosed a problem with compressor, which needs replacing. No mention of wanting to replace the dryer at the same time though- I thought that was a definite requirement when replacing a compressor.
    The dryer on this model is a narrow tube which is effectively just part of the condenser – is it possible to replace just the desiccant inside? Surely the whole condenser/dryer unit doesn’t need to be replaced?

    1. Hi Graham,

      That really depends on what is the matter with the compressor. If its a engagement issue no, if it failed and shot metal through out the system yes.

      Hope that helps


  24. You are good, and I hope you are getting some money for your knowledge? But I have a problem also on my o2 outback wagon with a 2.5, and hope you might help me. I bought this car 1 yr. ago and replaced the engine and what was needed at 159.000 miles. Changed receiver drier and checked clutch space on compressor, replaced belts, pulled vacuum on a/c and charged up to specks. A/C works fine, for a while in 90 degree temp. but driving along the air gets hot and it takes about 6 to 8 minutes before it gets cold again. When working, it blows about 35 to 40 on the a/c thermometer gauge (Igloo) brand, for a/c units. Comes back on and runs fine for awhile, then off again. Have you got any idea, (expansion valve) or what? Thanks

    1. Hello Tony,

      If you are able to determine if the expansion valve is working properly when it acts up? I bet its sticking when this acts up, gauge readings would revel this for sure.


  25. Hi Justin,

    Hope you can help me with some conflicting advice. I have a 2008 Impreza and the A/C compressor is not coming on and the weather is starting to get a bit warm. I’m hoping that it only needs a recharge but with the clutch not turning, I’m not sure of the best way to proceed. Some bloggers say to jump the relay to get the compressor going and add refrigerant but others say not to do that but to try and add some with just the key on and the blower fan running. Supposedly the system will then take some charge and then to go ahead and start the engine to finish recharging the system assuming the compressor comes on. So, jump the relay or no? What do you recommend? Thanks.

    1. Hi Tim,

      Jumping the relay without knowing if it has a proper charge of R134a is one way to damage the system. You really at a minimum need a set of gauges to know how to proceed with an AC diagnoses. The kits they sell at parts stores are bad news.

      I totally understand wanting to take care of it your self, but a set of gauges is a must.

      Hope that helps


      1. Hi Justin,

        Thanks for getting back to me. After doing some more research, I fully agree with you that trying to jump the relay is a bad idea. I did buy some DIY refrigerant and after adding some of it to the system, the compressor came on. Yay! However, it’s not blowing very cold so I’m sure there’s a leak someplace and I’ll be taking it to a shop as soon as I can. Thanks again for your input. Stay cool!


  26. Hi there. This is a situation where I would normally ask my dad for help as he’s a great mechanic but he passed away in December and I’m lost. I have a 2005 Outback XT. When we purchased this vehicle my dad stated that there was a bearing going bad with the A.C. because of the noise it would make every time it turned on. It would not reproduce this noise for the dealer of course. One year later it continued to make a loud noise every time the a.c. was turned on. I would have to turn it off when going through drive-throughs. It sounded just like a loud fan blowing. Almost a growl or grind. Hubby said it was probably just the bearing and it wasn’t hurting anything as the air worked great and was cold. Until yesterday. After turning on the a.c. to cool down the vehicle the a.c. squealed insanely loud for about 10 seconds and then it died. Completely quit blowing cold air. The fan is working fine but no cold air. The condenser continues to spin and make regular noise but now I’m terrified to drive it and cause more damage. The belt appears to be intact but I’m not sure what the squeal was or what to do now. I’ve read everything from bearings, clutches, hoses, leaks, belts, pulleys.. I’m just praying it isn’t the condenser as I know that will be expensive. My husband is capable of replacing parts and working on cars but he just needs guidance on where to start or what to look for. Any suggestions would be appreciated.

    1. Hi Jennifer,

      Sorry to hear about your loss.

      If the bearing is making noise in the AC compressor, it should not have been used until the compressor was replaced, as the bearing fails metal debris can enter the entirety of the ac system and do more damage that may require more parts to be replaced and or a flush.

      Ac is just not something a DIY should tackle at home. The R134a is not okay to vent into the environment, and without the proper recovery machine, you cannot replace any part of the “mechanical” AC system. I am sorry that I dont have better news but sometimes certain services are just better left to the Pros. It sounds like the compressor is failed, but I don’t know that without looking at it, it may have just had a low charge with also meant low oil levels in the Ac system causing the noise but because it was used rather than repaired its probably not going to be inexpensive I am afraid.

      Id suggest looking for a good Independent Subaru shop in your part of the country.


  27. I found you here looking for info to prep myself to return to dealer. I have two issues: the AC not working again when it was “repaired’ last fall, and dealing with a dealer. This is my 4th Subaru – technically the nicest and newest and ironically the one that has given me the most trouble. It is the only one I have taken to the dealer b/c of the warranty that came with it when I bought it used in 2013.

    The car is question is a 2011 Forester. The first time I did not have AC (59K miles) a mechanic friend recharged it and it was fine for the whole summer. When there was no cold air the following summer I took it to the dealer. (71K) They diagnosed it as having a leak in an o ring and recommended replacing the system. It was under warranty, – great news- except they did not have the part and wouldn’t for a couple weeks. I paid to have it recharged for the summer ( I am teacher and I travel in the summers) and brought it back in the fall to have it repaired, It is now summer, 8 mos later, and it is not working again. The receipt says REPLACE EVAPORATOR AND THE ORING AT THE CONDENSOR. My initial understanding from the service advisor was they were replacing the whole system.

    In terminology is stating “replace the evaporator and o ring” considered the whole system? I’d like your advice on what might really be happening to the car and what it might need to function properly, as well as advice and/or language for dealing with the dealer, which I am dreading: By the time they had the part and I was back in town, they said I had since timed out of the warranty by a few weeks. I pointed out they had documentation of the part failing while under warranty, and it was not fixed ASAP b/c they did not have the part. After many calls and emails it was passed on to me that they would repair as “goodwill” as I had not used the warranty at all for anything else.
    Now 8 mos later, there is no cool air and as a “goodwill” repair I do not know what ground I stand on bringing it back.
    Do you know if, in general, Subaru guarantees its service and parts? If so, for how long? How should approach the dealer with this? can you give me some possible “other problems” or terminology to help me ask the questions i need to to get to the bottom of this?
    And thanks for reading through this far.

    1. Hi JC,

      I am not 100% sure I understand the whole story here.

      So it sounds like it had a simple o-ring leak, it was recharged and it leaked out again which is not surprising, its kind of like having a leak in your tire and adding air but not repairing the hole in the tire and expecting it to still hold the air you just put in it. It than went to the Dealer, was diagnosed as having a leak at an o-ring plus the Evaporative core. Was repaired and 8 months later stopped working again?

      The Evaporative core is just one single component in the AC system, as is the o-ring, just one single component in a system with many parts and pieces. It’s not a good idea to let the ac system try to run when low on charge it will damage it. What starts out as a simple o-ring leak turns into a major repair later on in the Subaru’s life. Its not uncommon if the Ac system stays low for a while that over time many parts of the system will eventually fail, this is not unique to Subaru. If on a day the Subaru is looked at and the o-ring at the high side line at the compressor is replaced, the system is recharged and checked again for leaks, and none are found there’s not much else a dealer or a shop can do. If 6 months later it again is low, leak tested and a leak somewhere else is discovered well that’s just a new leak. I will again stress that if the system is ran low, it will most likely develop many leaks, and can develop many problems with the AC system. The Subaru dealer must warranty their repairs for 1 year 12k miles. If we have a car with an O-ring leak, we generally suggest all new o-rings or at least all in the same area as the one leaking.

      I recently posted a article just about the need for periodical maintenance on your Subaru’s AC system. AC Maintenance Article

      I hope this helps.


      1. Thank you, Justin this helps a lot. And you got the gist of it. The first time it was low I just thought it was time for a refill and did not consider a leak. When it was out the next season, I brought it to the dealer. What you said about replacing all of the O rings echoes what the dealer said initially, but that is not reflected in the final work order, which admittedly I did not thoroughly read when I picked the vehicle up. I was just glad – after all the warranty fuss- to have my car back and cool; I trusted they had done what was first proposed -replace the whole system- even though it took months of calls and emails to make it happen. I have emailed my same service advisor at Subaru but have not heard back. I will read through your suggested maintenance article for my own knowledge moving forward. Now that I am fully out of warranty I will bring it back to my local garage, who happens to have a great reputation for AC repairs. Thanks again for your thorough and prompt reply.

  28. does my 1990 legacy wagon have a cabin air filter? At 270,000 miles i should like to change it but can’t find it. Perhaps this will help the ac problems. the car has always lived on a long dirt road. . george

    1. Hey George,

      No cabin filters before the 2001 Outback VDC and LL bean, and even those were hit or miss.

      Hope that helps


  29. Hi Justin,

    I own a 2015 Subaru Legacy (84k miles), and have been experiencing some intermittent a/c issues since around August 2018. Typically the system works without issue but at times won’t turn on or barely pushes any air out. I can have it set to the highest fan speed and either zero air will blow out or barely any will — and then, randomly, later it will start working at the speed it’s set to. When air blows out, it’s always cool, just not always blowing out. This seems to mostly be an issue in warmer, 70+ weather when the car has been sitting outside in the warmth for a while; however, I’ve also noticed it a couple times when the system is set on defrost in colder weather. I’ve had air filters replaced within the last 8-ish months.

    I attempted to have a diagnostic completed at my local Subaru dealership sometime around October 2018. As soon as I arrived to the dealership the system started working just fine, and the rep told me that I should wait to bring my car in until the a/c was more consistently having problems. He said that if they ran the diagnostic and couldn’t find any issue(s), then I’d still be out the $135 diagnostic fee. So I opted to wait.

    Do you have any thoughts on what the issue might be for my car? It’s beginning to heat up where I live and I do a lot of car travel for my job. I must have reliable a/c in the triple digit summer heat. I have a message in to schedule a diagnostic and would love to go into the appt with a possible idea of what the culprit might be (and a possible price range of the cost to fix).

    Thank you so much,

    1. Hey Simonne,

      That sounds more like an Airflow issue more than it does an AC issue, or does the low airflow only happen when the AC is on?

      Low air flow could be the fan speed is not matching the command or there is blockage, intermittent blockage could only be from either frozen Evaporator core or a blend door that’s not working correctly.

      It would be better to have it looked at as its acting up, which might be hard. Dealers are not known for this type of flexibility.

      Its totally resolvable but is going to take some patience to get through.


  30. Hi I own a 2008 Subaru Impreza 2.5i. This summer I put 134 into my air-conditioning system. For the first time since I bought the card last November. I was pretty sure I put their correct amount in to 35-40 PSI afterwords the condenser kept kicking on about every 30 seconds. I spend the next few days letting some out because I thought I put too much in. After days of messing with it I basically just gave up. Now that it’s winter time and this is my first Subaru I didn’t realize that the compressor kicks on every time I turn the defrost on. Well with it being cold and when I first turn the defrost on in the morning my idol seems to be very erratic until the car warms up. So I thought maybe I would just let all of the stuff out of the land lines and start from scratch. And when I try to do that it was like there was nothing in the lines anymore. I’m fairly new to this air-conditioning thing I’ve only done it a couple times. I’m not sure why my air compressor kicks on every 30 seconds do you have any suggestions. Thank you.

    1. Hello Ayla,

      I would need the high and low side gauge readings, the outside ambient air temp and the screen shot form a Subaru select monitor or similar to begin to understand what might be going on with your Ac.

      My guess is that you do not have a full charge and the 35-40 Psi thing does not really add up to me. What is the running low side pressure when the ac kicks off, what does it recover to, what are the low and high side pressures prior to turning the car on, are they equal? What does the high side achieve prior to the AC compressor kicking off?

      If you fill an ac system without knowing how much is in it prior, recovering that refrigerant, evacuating air and moisture and then filling u to the proper capacity using a scale, and pressure readings you really have no idea where you are at. I understand they sell cans of the stuff at parts stores, but I don’t live in that world and it’s super tough for me to advise how to make that work for you I am afraid.

      Sorry I cant offer more help


  31. Hello. Issue is when it is 91 degrees out left two vents blow hot with recirc light on right vent over radio is coolest right passenger vent is slight cool. When it’s 79 degrees it is a comfortable ride. Took in two months ago the dealer did recharge package deal this is a 2014 Crosstrek one month later they measured coolant and ran for one hour reporting nothing lost. Now two months from initial visit it is the same initial symptoms. Is there a blockage issue or heat expand of seals issue. Any help would be appreciated.Ft. Pierce, Florida

    1. Hello Betty,

      It’s tough to be able to pinpoint that issue for you on your Crostrek without seeing some data like AC request and command as seen by the ECM. If the system is not low and still not functioning then the only option is a control issue or the AC compressor, should be straight forward to diagnose, but somebody has to be willing to spend the time locally to you.

      Hope that helps
      -Justin Stobb

  32. Hi Justin

    I have owned a 2010 impreza for about 2 hours! There doesn’t seem to be a problem with the aircon being cold but driving along I heard a pop then hissing sound & then a rattling noise like I’d just driven over a tree branch. I pulled over & the rattling stopped, was still ok when I drove away but hissing sound is still there. Looked under hood & only happens when air con is on. Air con still cold. Have you heard of this before & do you know what this could be before I take it back to dealer after the weekend? I’m afraid of being told everything is fine as it’s all working well but the initial noise was terrifying!! Many thanks

    1. Hello Stef,

      Possibly the pressure relief but there should have been some oil from the Ac system present if that’s what occurred.

      Hard to really now for sure with out hearing the noise

      Sorry I cant offer more


  33. Hi Justin, i’ve got a 2010 Subaru Legacy (BR) H4SO with an A/C problem. The clutch on the compressor engages initially (giving cold air) but after a few minutes running / revving dis-engages. The problem is it’s not being told to re-engage, i assume (because I put a volt meter over the a/c clutch solenoid circuit and no 12V reading there). Of note after a 4hr drive the other day going down a hill at speed with AC on, it kicked into life giving really cold air. This makes me think its one of a number of sensors. Which ones should I start by changing/testing in your opinion? I also have a crashed older model BP legacy I can scavenge sensors and relays from if any are the same. I have had it at our local subaru dealer and told them the gas was full and didn’t need re-gassing. They believed re-gassing would fix the issue so I authorised them to do so, which didn’t fix the problem. So they charged me for that as well as swapping AC control module but still faults and would like more time to diagnose at $110 per hour. Any help you can offer in the way of remedies or potential solutions other than going back to get bent over again would be great. Thanks

    1. Hello Dylan,

      Its really going to be best to have it diagnosed and repaired with a guarantee of repair then any more guessing.

      The car you have is not offered here in the US and I don’t know all of the inputs, or things such as does it have a rev sensor, has anyone measured the clutch gap?

      Sorry I cant offer more

      Best of luck, I am sure its hot there


  34. Please help! I cant find enough information online about my AC issue. I have a 2008 Subaru Tribeca with a plugged AC drain that makes the condensate leak into the car(passenger side). First few times I stuck a wire up the AC drain hose and unplugged it. When it plugged up for the third time, I used air pressure to unplug it. This time I removed a piece of palstic from the hose(was supposed to be there to narrow the hose, looks like) well…Its plugged again. From what Ive read so far, it looks like I have to take my dash apart, get to the main AC box and deal with refrigerant, which I know nothing about. Can anybody tell me exactly what’s going on and what options I have?

    1. Forgot to mention- other than the condensate leaking into the car on LEFT TURNS only, AC and heater work great, always have.

      1. Hello Elena,

        The Evaporator Core Case would in fact need to be taken apart to look for debris clogging it, there really is no other way I am afraid.


  35. Hi Justin,

    I’m in a bit of a state of depression, $1350 in the hole;

    My AC had catastrophic failure after an oil change at the dealer, compressor spilled it’s guts. As expected, dealer suggested full system replacement.

    Had first mechanic replace compressor with OEM, aftermarket condenser, drier, expansion valve and all seals. Also made sure they evacuated and flushed system before installation of new parts. AC failed after 30 mins, after efficient cooling initially.

    Next mechanic found no leak. 3rd mechanic found low refrigerant (likely undercharged by mechanic 1 he says) and recharged, also tested vacuum for 30mins which fully held. Was able to fully recharge with 13oz and found the original issue after part replacement returned; AC blows hot after 30-45 mins. He replaced high-side line and pressure sensor with new OEM line from Subaru. Recharge and test again; same issue; 30-45mins in hot air blows.

    I’m running out of money, mechanic 3 says replace compressor again as after the last refill and series of pressure tests we saw 350PSI on the high side and normal on the low. I’m thinking it could be a stuck expansion valve, but I’d like a way to test this, especially as the part is new. Could there be an issue with the condenser as it is after the compressor? It’s been hot in Chicago for a few months now and not having AC is awful, but I’m reaching the breaking point and this has been 2x the budgeted cost.

    Plan D is to take it to Subaru for a diagnostic, but I don’t trust them and expect they’ll tell me to take everything out, drop in $3k in Subaru parts and it’ll work…not an option..

    1. Hi Nearing the End,

      Ive been on Vacation with the Family and so I am not sure if this will do you any good at this stage.

      Anyways.. So if I understand the AC failed, was diagnosed at the Dealer, repaired somewhere else where they may have not actually diagnosed the issue themselves, when it didn’t work they threw their hands in the air, you took it to another shop who said the new Ac compressor has failed? If this is accurate what a mess.

      I cant know from here what it needs, but you need to pick one shop and one shop only to service your Subaru, I go to the same Dr, Dentist and Hair Salon, well when I had hair that is. The problem with having it looked at at Shop A and repaired by Shop B is who is going to stand behind the diagnoses?

      If I had to guess however there is some debris in the system.


      1. Thanks Justin.

        Yes, I had a few shops take a crack at it. Since my last post I replaced the expansion valve and condenser again with OEM parts, checked all seals, connections and electrical connections, this time on my own as I’ve become quite familiar with the workings of the system. Most recent mechanic did a second evac/recharge, system still experiences cycling compressor when not idling, only cools at initial run. I also replaced the AC relay as I read they had a history of issues.

        There was no indication of debris inside the system during my inspection, the point of disconnecting both high/low side lines before my last compressor replacement was to investigate this theory and blow out anything that was present.

        I’m thinking there could be an electrical issue at the control module for the unit, or something that would cause the system to believe full-throttle is open when RPM is above 1k? The only area which is unfamiliar with me is electric on the AC system, and frankly that’s why I now question it…Is Subaru the recommended choice for looking into possible electric issues with the AC system?

        1. The next step if you think its electrical is to understand if the computer that turns on the Ac thinks its on or off when its not working.

          If it thinks its on and its not why?


          1. Hey Justin,

            So I ended up pulling my climate control/radio unit and replacing it with a low-mile OEM unit (and did the aux line into FM radio hack while I was at it) and guess what…the cheap ebay OEM replacement seems to have fixed my issue. Unbelievable! There must be some sort of sensor or calculation that happens in the head unit that controls AC cycles.

            Even the mechanics I mentioned it to were surprised.

            Might be moving to Seattle, if I do I’ll be sure to stop by for the 210k timing belt change.

  36. Hi, been looking on several websites with all similar AC problems. This one seems to be the only one with answers:-D
    Ok, read everything on here. Got a 2006 Forester, manual trans, non turbo, had since new. 155k. AC was serviced last year, replaced high side hose & O-rings, evacuate & recharge. Now, like so many others, AC blows fine till it warms up outside. Used to quit blowing cold at 105 degrees & above. Turn off AC switch for 60-70 seconds, blows cold for a few miles. Lasts up to 20 miles on freeway. Took to my regular mechanic. The owner didn’t work on it, but had a lesser experienced “kid” work on it. Said it was the clutch. Can’t find just a clutch, have to buy compressor. $1200.00!! Um, no. Well, he then found a clutch. $656.00. Problem still there. Took it back, he drove it 4.5 miles on freeway, temp varied between 40.6-48.3. After 1 minute idling in their bay, 46.4. 2 minutes, 48.3. Says system performing well at this time. (Not much of a test eh?) he did say he put Gage’s on it & all was good. Says its compressor still. From my experience, a compressor either works or it doesn’t, yes? It’s controlled with switches, relays, etc. & no, that’s clown didn’t check the old clutch before replacing it. Now it seems to start messing up at lower temps, say 95. From my readings, temp blows from vents about 45. When compressor stops turning, it gets up to 70-80, then depending on outside temp, say 115, it blows 95-100. I have found another shop, problem is I use car for work driving all over town. Haven’t been able to get it down there yet. Got any ideas? Doubt that shop checked any relays, sensors or anything of that nature.

    1. Hi Dan,

      It must be diagnosed when it’s acting up, there just isn’t the information here that is needed to know whats the cause, such as when it stops working is the Ac clutch engaged, if it is whats the high and low sided pressure values, if it’s not, what does the ECM think is going on, does it see the AC request? Does it think the AC is on?

      A improperly installed clutch could cause the exact same problem it was to solve if it wasn’t “gapped” properly and it would be temperature affected. The more it expanded the more a slightly out of adjustment clutch would reveal it self.


  37. Hi Justin,

    I just found you online – maybe you have some insights on the A/C problem I’m having with my 2009 Subaru Legacy (155,000+ miles).

    As the temperature started getting hot this summer, I noticed that my A/C wasn’t keeping up. Sometimes it came on, sometimes it didn’t. When it became unbearable (e.g., after leaving my car in a parking lot all day with 90+ degree temperatures heating up the interior) I brought the car to my Subaru dealer. They said the compressor was overheating and I needed a new one. OK, did that ($$$).

    The next day the A/C was still operating intermittently so I brought the car back to the garage. Dealer said there was a bad O-ring that needed replacing (thankfully, no charge). The next day (temperature still in the 90’s), I’m experiencing the same intermittent A/C behavior as before.

    One thing I noticed (and am watching carefully now to see if it is a pattern) is that when the car is stored in the (cool) garage overnight the A/C seems to work fine if it comes on initially W/O recycling. However, if I leave the car in a parking lot where it warms up and the A/C starts recycling when I start the car’s engine, I don’t get A/C (just warm, humid air and the fan going full tilt). Manually turning off the recycle does NOT bring the A/C back (so the recycle status may just be a coincidence).

    Have you heard of any Subaru A/C problems that are related to whether the air is recycling or not? I’m grasping at straws here and will be bringing my car back to the dealer for a 4th time (same issue) in 2 days.

    1. Hi Lisa,

      I think you mean the Recirculate feature? This is when you limit the fresh air coming in, say on a really hot day as the warmer the air coming into the cabin the harder it is to cool the cabin. So yes a AC system with an issue, may work better using the recirculate feature, but shouldn’t be the other way around unless there is an issue with the Ac control module or an input from say the ambient temperature sensor as just one of many possibilities.

      Because you obviously have paid a lot of money to not have it repaired, you really need to hold the Dealers feet to the fire, and make them resolve this for you. My guess is it was misdiagnosed prior, what must be done is a diagnoses of the system when it’s acting up.

      Hope that helps


  38. Hi Justin, wish you were here in Eugene! Took our ’99 Impreza to local shop. He replaced the compressor. Fan blowing loud, but only a trickle of air coming out the vents, and the air is cool, not cold. What do you think? Thanks. Jeff from Veneta

    1. Hi Jeff,

      For the Air flow issue

      Id say the blower motor has an issue or there is blockage in the ac/ heater case somewhere.

      For the air is cool not cold, you might still have an AC issue, I would go back to the shop that just repaired it and inquire.


  39. My entire interior heating and cooling system stopped working. Had the a/c on when suddenly went out…completely…no light, no air movement…nothing. looked at fuses. Replaced the main fan relay fuse and got lights on dial back, but still no air movement. Can hear the air compressor turn on. What could stop air flow like this? Thank you.

    1. Hello Taila,

      That does not sound like to much fun.

      If there is no air flow perhaps either the Blower motor has failed or doe not have the proper power to it to turn it on? You could stat with checking the fuses.


  40. Wow I’m surprised how long you have responded to questions. Thought this was old info but maybe you can help me too :D.

    I have a 2002 Wrx which the compressor keeps kicking on and off rapidly when it reaches operating psi in the system. I have replaced the evaporator, expansion valve, and pressure switch. The compressor was replaced last year and the AC worked all summer. This summer it didn’t work because I’m assuming it all leaked out as I smelled refrigerant inside the car last year. I know there is a super small leak(size of a paper clip needle or smaller) at the low line behind the intercooler. There also may be a slow leak at the expansion valve o ring because the car lost vacuum, however it was a slow change.

    My question is, even with the leaks if the pressure built to the proper psi, shouldn’t the compressor stay on until the pressure goes below operating? Any other reasons why the compressor could kick on and off rapidly (meaning within seconds)? I have jumped the compressor at the pressure switch and it runs so I believe that means the compressor is good.

    1. Hey Phil,

      If the system is low it can’t function properly. You cant be running at the proper pressure if its low, its not possible, something suffers. Also the R134a is the lubricant, so trying to use it when its low will damage the system.

      Also look into

      TSB 10-72-02


  41. I drive a 2009 Subaru Outback. My ac works intermittently. Some days it will run blowing cold air for an hour, sometimes it only runs for 5 minutes and sometimes it doesn’t run at all. Changing the temperature setting does not help. The system is fully charged. What are some troubleshooting ideas you would recommend?

    1. Hi Kat,

      When its not working, someone needs to figure out why.

      **Does the ECM think the AC is on or not?
      **If it does and it’s not on, why?
      **If it doesn’t see it’s on, does it see the Ac request form the Ac control?
      **If there is Ac Request but no Ac command, why?
      **If there is Ac Request, and Ac Command and it is still not coming on, why?

      First place to start is with looking at data with the Subaru Select Monitor.

      Hope that helps


  42. Justin, I would disagree that losing a few ounces of refrigerant each year should be considered normal. I bought a C240 and a Silverado new in 2002, and neither has ever required any sort of service to the A/C other than cabin air filters. I live in Phoenix, and both work flawlessly in rush-hour traffic and 110 degree heat, in spite of being 14 years old. Not so with my 2015 Forester… I have to rev the engine to keep reasonably cool at stoplights, which irritates the hill hold system. Either low on charge, or the compressor pulley should have been smaller. Dealer says it’s perfectly fine…

    1. Hi Paul,

      So While I appreciate the comment, and I understand your frustrated with the AC on your 2015 (which sounds like there is an issue with by the way) I just need to put out some facts for you.

      Fact.. SAE (Society Of Automotive Engineers) determined a long time ago that an acceptable rate of loss of Ac refrigerant is 1/4 ounce per year at any fitting, most vehicles have about 8 fittings so the industry norm is around 2 ounces of loss per year. This is what is taught at the professional level including by IMACA now MACS. Some cars will loose less and some cars will loose more.

      Fact.. The ac system may not suffer any change in cooling until the system is as low as 40% below maximum capacity, but will loose oiling and lubrication to the Compressor which can cause premature failure of the Ac compressor.

      Fact.. The Ac system in the Chevy and Benz are much larger than the Subaru in terms of capacity, so unless you actually do an evacuation of the Chevy or the benz, and measure what comes out you do not know if its low you are merely assuming because it works it is full, which one day will create an issue with the compressor.

      If a system holds 2 lbs or 32 0z like your Chevy, it will take 16 years to be empty and about 10-12 years for it to be noticeable, due to the lower pressure creating less loss over time to reach the approximately 40% low. Equalization pressure can change from 70, to 60 to 50 etc, the less pressure the slower the potential loss will be. A system with low pressure will have a greater “on time”.

      I hope that clears up the facts around refrigerant loss in a car.

      But aside from that you do seem to have an Ac issue that I would Contact SOA about.

      Hope that helps


  43. Hey,

    I have a 2004 Legacy Outback, I was wondering if the AC controller unit is interchangeable with the 2006+ manual AC controller. Trying to upgrade the head unit and dont want to pay hundreds for a Fascia kit.

    thanks heaps

    1. Hello Shannon,

      No they don’t interchange, wouldn’t physically bolt in place.

      The 2004 shouldn’t be expensive to add an aftermarket deck to?


  44. The noise seems like water slushing around & I am most worried if this could be an expensive problem. Thanks for your time & reply.

  45. During the past week I noticed a sort of clicking noise coming from the dash, and then the past 2 days have heard a sort of slushing noise like water. The vehicle is a Subaru Liberty 2000 sedan, fully serviced by the same mechanic since new. What could be the problem with the aircon & would it be a major job. My only car since purchase until my death as pensioner now. Sydney Australia.

    1. Hello Judy,

      No idea on the clicking as there is just to many options to choose from, the slushing noise is most likely air in the cooling system or low refrigerant levels in the AC. The heater core and Evap core are both inside under the dash, low levels in either system can make a noise like you describe.


  46. Hi Justin, I have a 97 legacy outback. Earlier today the a/c was working fine. Got on the freeway later, regular warm air started blowing out, and the temp gauge spiked to the top. I turned off the a/c, the gauge returned to normal (halfway up). When I idled, the gauge would slowly rise to almost 3/4. After resuming speed, it goes back to halfway. Any ideas on how to diagnose or fix this? Thanks, Glen

    1. Hi Glen,

      You have a cooling system issue that needs to de addressed. Might just be low, or it could be something more serious.


  47. I have a 2003 Subaru Forester. AC ice cold. But it feels as if Blower motor is not blowing hard at all. When its on max blow at 4 it feels like 1. Any ideas before spending money on new blower motor if that’s even the problem

    1. Hello Jon,

      It would need to be tested, it could be the ballast resister, or the switch and most likely not the fan.


  48. Hey Justin,

    I have a 2008 legacy. Last year I had the blower motor replaced, which is still working fine. However, the temperature control know recently became rigid and resisted turning from hot to cold. The knob is now less rigid, however it will not turn all the way to the coldest setting.

    Also, when turning the knob to the heat setting, there is a thud about half way through the turn. If the blower motor is running and I try the temperature knob back to cold, no cold air will come out. I have to turn the blower motor off and then turn the knob to cold, and when I do so there is the sound of a latch or flap closing.

    I am not sure what the issue is or what to do. Any help or advice is greatly appreciated. Thank you for your time.

    – Jon

    1. Either the blend door or the cable is having an issue, needs to be looked at.

      Most likely the cable is binding or is bent?


  49. Hi Justin,

    I own a 2006 Subaru Forester Turbo. The AC has not worked properly for about a year in that it runs for 20 minutes or so and then blows out hot air on auto. I just had Cityside Subaru in Belmont replace the condenser and 0 rings, but it is still doing the same thing except that now it does not work at all. I will take it back to the repair place, but was wondering what my conversation should be like with them so that I don’t have to go back and forth many times. thank you

  50. Hello Justin
    I’ve a Tribeca 2009. Recently, a problem has occurred where, when I start the car, it blows hot air. After around 5 minutes or so driving at around 50 mph approx., it starts cooling. If I stop at a traffic light, the intensity of the coolness decreases. If I idle the car at the grocery store for around 10 minutes, when I come back to the car, I can see that there’s hardly any cool air from the vents. If bad luck could have it, right from the time I start the car, if I have to be around town, stop drive stop drive kind of a situation with max. speed of 35 mph, I have had it for that day. Any suggestions on where to look for the problem?

    1. Hi Mike,

      Thats something that needs to be diagnosed locally I am afraid. We do see some issues with the climate control module on the Tribeca’s here and there.


  51. Hi,

    I own a 2006 Subaru Forester Turbo. The AC has not worked properly for about a year in that it runs for 20 minutes or so and then blows out hot air on auto. I just had Cityside Subaru in Belmont replace the condenser and 0 rings, but it is still doing the same thing. Works fine for 20 min. then hot air. I will take it back to the repair place, but was wondering what my conversation should be like with them so that I don’t have to go back and forth many times. thank you

  52. Hi I don’t know if anyone can help me or not. My 2001 Subaru outback sedan’s a.c. stopped working about 1/2 yr ago. The knob to turn the temp. to colder (not the dial with the numbers, it is the dial to control the coldness and hotness) is difficult to turn. My mechanic said he did not find a leak, and that my control panel may need replaced. Is this common in this yr make and model? Do you have any suggestions on how I can fix this problem?

    1. Hello Tarah,

      If the blend door control is difficult to move it could be in the control panel. Without seeing it I cant really know if that’s it however, your guy should be able to give you a proper diagnoses however.


    1. Hi Carl and Justin, i have the same symptoms in my 2010 Impreza.
      Mechanics couldnt diagnose yet.
      Could you tell me what was your issue (if you remeber).



  53. I have a Subaru outback sedan 04 losing ac at 45 mph drop speed to 40 mph and it comes right back? Belt is tight, purged (to a recycler) pulled vacuum on it over night it held put 24 ounces of 134a in it .High side pressure reading 180 to 230 depending on rpm low side reading around 40 to 60 again depending on rpm. it just shuts off at 45 rpm dose not matter had it in natural going down a hill rpm at idle still shuts off at 45 lifted it up all four wheels off the ground ran it up to 45 it shut off definatlly speed related not rpm??? HELP!!

    1. Hi Carl,

      There are lots of possibilities, its not going to be a basic issue with the ac system it self unless it’s overfilled, which based on your gauge readings is quite possible, it could be an input from the TPS to the ECM, could be a rev sensor issue.

      When it stops working have you tried to figure out if the compressor is being commanded on by the ECM?


      1. did not hook a computer to it yet, but the tps,that would be throttle related wouldn’t it ?you can be rolling down a hill in natural rpm at idle and at 45 it shuts off but what is a rev sensor never herd that before is it a Subaru thing?

        1. Hi Carl,

          Yes the TPS is Throttle Position Sensor and @ WOT, (Wide Open Throttle) the ECM (Engine Control Module) cancels any valid AC on request.

          The Rev Sensor is the Revolution Sensor, and it tells the ECM if the Ac compressor is engaged or not.

          the AC system is just that “a system” its just not as simple as it has a charge of refrigerant or not. That only covers 25% of the system.

          There is just about no way you can diagnose any situation thats not “its got a leak” type of a situation with an AC system without hooking up to the ECM, it’s ultimately what controls it. Seeing what the ECM sees when the AC is not on is key, what if the ECM thinks its on and has no idea its not?


  54. I also have a question about my cooling system on my 2000 outback has 220.000 miles. It seems when the radiator is full and engine gets hot it sometimes spills over into the overflow but then gets hotand does not siphon back to the signs of coolant in oil or visa versa looses coolant from radiator flowing into overflow when hot any help would be appreciated. Thanks

  55. Justin, I have an 05 Subi Forester XS and started have AC problems would blow cold and then go off for about 15 to 30 minutes and maybe come back on. Took to Dealership and they could not find anything wrong. Won’t even blow cold on defrost. They checked the freeon and was full. Changed out the pulley to tighten belt, which was broken, and no change. Have never had anything wrong with my car before. This is the first issue ever. Do you possibly have any suggestions?


    1. Hello Sheila,

      The common thing for the Impreza/Forester platform is a failing expansion valve. I imagine the dealer didn’t spend enough time with it to get it to act up.

      It needs to have gauges hooked up to the system when it acts up to confirm this.

      Hope that helps


  56. Justin, I have quote for repairing ac system on my 2004 Subaru Outback 3.0 L 2999 CC H6 DOHC 24 VALVE; 165,548 MILES;
    GUIDE A/C COND HOSE R&R $ 47.50
    LOW SIDE LINE $ 226.05
    RECEIVER DRIER R&R $ 47.50
    LABOR $ 280.45
    PARTS $506.75
    TOTAL $810.00




    1. Hi Lynn,

      The leaks should be addressed, the system evacuated and recharged and the compressor assessed from there. The H6 models also have a rev sensor at the compressor that can trip guys up a bit.

      But yes repair the leaks and go from there is the right way to go about this.


  57. Justin,
    Do you own a repair service and actually work on Subaru’s ? I want you to work on my Subaru !!
    Thank you.

    1. HI Lynn,

      Yes, I have worked on Subaru’s since the early 1990’s, I have owned All Wheel Drive Auto in Kirkland Washington since 2005.



  58. I have a new 2015 Forester XT. When accelerating, the air-conditioner fans noticeably slow down. I’ve checked the voltage while driving and discovered that the voltage also decreases significantly when accelerating. The voltage has gone down to as low as 11.3V at 2,000 RPM. What’s wrong?

  59. Hi Justin,

    I have a 2010 plated imprezza. AC has just gone on me. official part that needs replacing ive been told is around $900 for the part alone. non official part is around the $350 mark but is not in stock until Nov which is too long to wait. do you know if the whole dash has to be removed to get that particular part in behind and advice on should i wait until Nov?


  60. Hello Justin. Hopefully your knowledge of a/c will prove invaluable. I start my 2008 Tribeca, 48000 miles. Set a/c to auto, lowest temp, highest fan setting. And the a/c blows super cold. Visually the clutch engages and fans spin. After 5-10 minutes of idling i will get hot air blowing. Seems to be hotter air blowing then from the outside, temps outside 80-85F. I notice that the clutch is no longer engaged and the fans still spin. After this i repeat the entire process an hour later and still same as stated above. Any Information you have will be helpful.

    1. Hi David,

      There are a few possible things that could be wrong, the place to start is while monitoring data on a scan device you need to see what the command of he ECM is when the AC is not coming on.


  61. Jason, I have a 2000 Sub Outback Wagon, with about 185K on it, have had it about 3 1/2 years, wonderful vehicle. AC needs to be charged every year, but has worked wonderfully no issue until about 5 days ago. While on a family trip to New England (the whole journey about 2000 miles)the bearings on the ac pulley went, broke the belt. Fortunately, there was a Subaru dealer in Andover Mass, I was able to procure a replacement pulley, mounted it on the bracket,tighted the belt and the ac worked fine again. Then 5 days ago, my daughter and I heard what sounded like moaning and a popping sound and a squeal from the engine compartment. When the ac button was turned off, no noise. Turn on, the noise was back. When I looked under the hood, what I saw was the ac clutch spinning/engaged but then would almost skip or stop…this was the culprit of the squeal. Is is the tension of the drivebelt perhaps? Or is something wrong with the clutch as a result of the damaged pulley? When the clutch engages correctly and the compressor spins, the ac is nice and cold, but when this squealling happens, the air is not cold, the moaning and popping happen which all stops when the ac switch is turned off. I’ve replaced the clutches on other cars when they were worn (since it does have 185K)but there do not appear to be any clutch kits available for this Zexel DKV14G compressor. If the relay were faulty,would that cause this type of phenomena?

    1. Not sure who Jason is but I will go ahead and answer for him.

      The ac system has had a leak that you let go unpaired, most likely from the hoses. I would suggest what ever you do you also correct the leak as it should not need to be recharged every year. I can’t know from here if the belt is loose or the clutch is acting up, but yes for some compressors there is not a replaceable clutch or at least one you can purchase.


  62. I have a 2010 Subaru impresario the account blows cold and hot air,kicks on and also seems to blow hot air on or off and at any control can you please help.

  63. Hello Justin,

    Trying to help cousin with her car, 2004 outback H6 3.0. Her A/C wasn’t cooling well in May and had an Independent check it. Said it was low on 134, gave a boost that helped a few days. She returned and he added more with a stop leak that didn’t cure the problem.

    Next she carried the car to a Mechanic known to work on Subaru and he told her that the first guy didn’t help by adding sealant, needed new compressor and the repair could be $1,400.00.

    She can’t afford that right now and I wanted to help. couldn’t hold vacuum so disconnected compressor. The rest of the system was tight. Located this site and your comments, reconnected compressor with new O-rings and the system is holding well.

    Car has 145,000, was maintained by Dealer for her Mother. Oil in ports was black but no visible metal. Should the system, be flushed before trying recharge since the stop leak was introduced, could it compromise sensors?

    Thanks, Oscar

  64. Hi Justin- Thank you for all your great advice. The AC compressor clutch may or may not start/run when it should such as when I press the AC button, when I put it on defrost or just when it is generally hot in the car. It is a 2012 Forester Limited. The dealer tested the climate control and confirmed 44 degree air from vent when it is working. The problem seems worse when first starting car maybe up to ten minutes of driving in hot car or with foggy windshield and then compressor kicks in. Thanks for any advice. Robert.

    1. Hi Robert,

      Thats going to be a challenge to help with. I can lay out what we would do, but no flat rate technician at a Subaru Dealership is going to bother with it as he or she isn’t going to be paid to diagnose the issue, it’s just how the game is played Manufacturer/Dealership relationship.

      I would say that a few trips plus a call to SOA will be what it takes to get to the bottom of it.

      My guess is the ECM is not commanding on the AC intermittently as a result of a command cancel program. This would be at WOT, (Wide Open Throttle) for example on every car but also under some temperature readings. So if a temperature sensor input is off for a bit it would cause command cancel.

      The only way to figure this out is to have the Subaru Select monitor on the Subaru looking at the AC data command data while it’s not working, if it happens to work when the Tech looks at it, well it’s never going to be resolved.

      I am guessing its the ambient Temperature sensor from here based on your description, but there are always other possibilities.

      Hope that helps and stick with it..


  65. I have an intermittent AC problem on my 2005 Subaru Outback LL Bean edition. When it works, it runs fine with plenty of cold air. If it doesn’t work it just blows hot air. Its about 50 to 50, working or not.

    I have the problem diagnosed (its a guess really because they cannot confirm the problem) as the face plate controls which include the CD player and radio in the car. The quoted price to fix is $670 with no guarantee of fixing the problem. That’s alot to spend for a potential solution. Any tricks to actually diagnose the problem?

    1. Hi Dan,

      It can be diagnosed, not really any tricks its actually called knowledge and skill. Some shops employ Technicians that can figure things out, some do not have those type of employees, some shops have no issue explaining to you it costs money to diagnose problems, some struggle to explain that properly.

      Ac is the single toughest system to try and explain to a customer because quick lubes offer “AC services” for cheap and for many drivers that’s actually all the car needs, but for some it actually has a real issue that needs a skilled pro to diagnose.

      On the H6 models have replaced the climate control unit like you have mentioned but also the Rev sensor and other items as well, each time a diagnoses was done to obtain results. I am sorry that’s not the place your in right now.


  66. I have a 2004 Subaru Legacy and I just had the AC compressor replaced and system checked at the Subaru dealership but I’m still experiencing the same problem. They told me that they ran the AC for 2 hours and it was cold and full of freon. While driving my AC stops blowing cold air at random times when it’s hot outside and I’m starting to think that the compressor wasn’t the problem after all. I read in the manual that the compressor turns of when the engine is working hard(like going up a hill)but this happens when I’m stuck in traffic too. Please help me understand what can be causing this to happen.

    1. Hi Lucas,

      You need to go back to the Dealership and let them know there is still an issue. I just can’t diagnose the issue from where I am, the possibilities are just to many. Yes at WOT (Wide Open Throttle) the AC is commanded off, but the key is to see when the ac is not coming on what is the command and status of the ECM. That’s the only next step.


  67. Hi Justin,

    I just bought a 2007 Outback in a private sale. The AC seemed okay when I test drove although it wasn’t blowing freezing air and ambient air was in the 70s so it wasn’t being stressed. Today was a 95F day and the AC seemed like it was barely working. I’m not a professional so don’t have gauges but did make the following observations:

    1) With the car running in the garage (back end out the door) and ambient temp at 80, the pressure hoses were too hot to touch and the suction hose was just barely cool. I compared this to my 98 Camry sitting in the same garage where the pressure hose was hot and the suction hose was icy cold and dripping moisture. Could this indicate low refrigerant level? Or does it sound like some other problem?

    2) Inside, with both driver and passenger temp levels set to 65 (the coldest setting), I measured an outlet temp of 73 on the driver’s side and 53 on the passenger’s side. Recirc was set to fresh air. The air from the driver’s side also had a humid smell consistent with lack of dehumidifying while the air from the passenger side smelled cool and fresh. Is this more likely to be a controller problem or a problem with the mixing unit? Any suggestions for how to troubleshoot are appreciated.


    1. Hi John,

      It could be low on R134a but it could also be the Expansion valve. If you had gauges, it would be fairly easy to spot with out all you can do is try one or the other.

      I have to stress there are other possibilities as well, just giving you a couple scenarios.


  68. Hi I have a subaru 2005 legacy limited that I have had ac issues on again off again charge is good no leaks. Then I noticed the clutch not moving so checked for power to the relay was good figured I had a bad relay so I bought one installed it still not functioning quite right. I had the ac running as i pulled the relay out and noticed the clutch engaged when the relay was half way out pushed it in clutch stopped started to pull relay out clutch would engage BAD (loose) terminal connection tightened conn works weather the relay is seated or partially seated cross your fingers that it holds and that this helps you.

  69. I have an 03 H6 Outback.
    Pressure at low side is 50. When I turn on AC the compressor starts and then shuts off. Blow hot. I just replaced the large hose to the evaporator/fire wall and recharge the system. No codes are showing up. Should I replace pressure sensor on compressor and/or AC relay? Or is there a test?

    1. Hello Mitch,

      I would look at the Revolution sensor as one possibility, if you have a Subaru Select monitor or equivalent you could see if the sensor is sending a Signal to the ECM.

      That’s where I would start.


    2. Have the car running with the ac on in auto mode. lift the hood locate the ac relay. It should look like a small box approx 3/4″x 1″ lift it out while car and ac on aand listen to the ac clutch to engage, this is how i found that Mine had a bad contact relay to fuse box when i would try to remove the ac clutch would engage when I fully seated relay ac clutch stopped repeatedly and consistently. tweaked the female conn end for better contact and now no matter what i do to the relay wiggle etc (aside from removing it) the ac works the way it should.

  70. I have a 01 Outback H-6. My A/C works fine for about 15 minutes after starting the car, but then the vents start blowing warm air. If I turn the car off, even for the time spent at a stoplight, the problem repeats again

  71. I have an 2008 Tribeca 110k miles. I started having trouble when making turns with the AC on it seems like there might be some sort of door closing that restricts the air on the passengers side. Then most recently when I started the car and turned the air on high/low I had very little air coming from the front vents. The back cabin air was working as normal I switched from defrost, vent, floor with no luck. Any Ideals?

    1. Hello Keith,

      It’s possible the climate control unit is having some issue. Not knowing your capabilities it’s tough to tell you what to do next? Are you comfortable taking the dash apart?


  72. Hello,

    I have an 06 legacy OB wagon with 97k. The a/c blows cold and then for about 10 seconds warm and then back to cold and so on and so forth.

    I had the r134 checked and it was good, no apparent leeks,
    same results.

    When I have the car idling in the driveway the a/c does not click off as much, but you can still see the clutch disengage with the a/c knob on high.

    Someone on one of these forums mentioned a pressure switch?

    There is not a suby dealer within 300 miles of me.

    I also heard of the a/c being bad, I pulled another fuse and same thing.

    Any help or direction would be great.

    Thanks In advance.


    1. Hello Davezeus,

      I would look for an import shop if there is no Dealer in 300 miles?

      I can’t guide you through an entire AC diagnoses with a multitude of possibilities, yes there are pressure sensors, but the place to start is to look at what the BCM and ECM are seeing.

      The computer ultimately controls the AC function, I have seen a engine related sensors create AC on time issues, as well as AC pressure sensors, modules and revolution sensors as well as mechanical AC issues such as worn clutches or sticky expansion valves or failing thermistor.

      Sorry I can’t offer more.


  73. Hello,
    I have an 06 legacy outback! My a/c will blow real cold and then warm for about 10 seconds and then back to cold and then warm again and so on so forth. I have had the r134 checked and it was good, does not seam to have any leaks.

    When the car is at idle the compressor seam to run for awhile and then after awhile it will click of for about 10 seconds and then back on, if you rev the motor to 2k it is more frequent. Some one mentioned a pressure switch.

    There is not a suby dealer for about 300 miles from me.

    Any help would be great, its hot in Arizona!!

    Thanks in advance

  74. Hey Justin,

    Thanks for the excellent article! I have a 98 Legacy 2.5 that doesn’t blow cold at all. So far what I have done is test the low side pressure with a cheap gauge that comes with the refrigerant, but not adding any refrigerant. Thing is that the needle goes to the red zone instantly and doesn’t move even when the compressor is on.

    This system used to work fine before, then the compressor locked and tore a belt. I could tell it locked because the belt was burn in one location when I grabbed it. Weirdly enough after the belt was tore the compressor was moving freely. I replaced the belt, but nothing happened.

    I’m sure the compressor is trashed and will get a rebuilt one off e-bay. Is that a good idea? I will also change the drier. The thing is that I’m afraid of having debris all over the system and it’ll only cost me more 100 bucks to change the evap and condenser for new ones. What do you think about this?


  75. Hi,

    I have a MY03 Impreza STI, but light version, so no AC. I did get one used from another STI and have installed this one in mine. As mine is a light edition, it has the manual climate control (not running the automatic one). The thermistor on the automatic I did get the AC had a plug with only 2 positions (and 2 wires), but the one available in mine has 3.
    I was looking at in order to try to find the correct thermistor, but it seems I’m missing something else.
    Does someone has the complete wiring ?

    1. Hi Nicolas,

      In the US the first year of the STI was in 2004, I can only assume you are writing from another country? Sometimes trying to add a system that did not exist can be a challenge, did you look to see what the Dealer installed AC option cost? That doesn’t mean you have to have it installed at the Dealer just that there may have been a kit that would have been more plug and play.


      1. Yes, correct, writing from France, and I’ve finally found the missing part on IWSTI. There, the STI was first introduced in 2001.
        For information, manual AC need another evaporator thermistor then the automatic one.
        “Thermoswitch” Part# 72166FE010 is the needed one instead of Part# 73540FE000 for automatic.

  76. Hey Justin,

    Great page! Lots of great info.

    My question is I have a 2003 forester automatic with mechanical a/c controls and after this winter in Colorado I no longer have cold air when the a/c is on. It has worked great since I bought it five years and had finally given out. I have verified that the compressor is working so my thought was a leaky line or just ask out of freon. I was a mechanic in my past life and I would like to figure it out myself. What tests can I do with what tools before I let someone else lay a hand on my car.

    Thanks Zac

  77. I have a 2000 Subaru GT wagon H4 w/245K miles, auto trans replaced under warranty @ 60K miles, suffers intermittent blown AC/blower fuse under acceleration (seems close to or at shift point.) AC blows cold, car lurches when fuse blows likely from AC clutch disengaging. Problem started @ ~180K miles and has increased with mileage.

    Had previous diagnostics run, unable to duplicate problem, no other issues or codes. Seems to occur most often when car is heavily loaded or when driven more aggressively, especially at the 2nd to 3rd shift. Doesn’t seem to occur when only the blower (No AC) is on.

    Transmission does shift somewhat ‘hard,’ especially when starting from park & shifting into reverse, producing a fairly loud ‘clunk.’ Both transmissions (original & replacement) always somewhat balky after first 40K miles.

    Live in California, so AC gets constant use. Possible AC clutch and/or relay or other? We keep a box of 15amp fuses and can swap in less than 1 minute once stopped…, but tired of this. Recent 250 mile, 6 fuse weekend trip with heavy load.

    Thanks in advance,


  78. PS – Didn’t clearly state that this fuse blowing symptom/issue seems to occur during or immediately after the shift and that this is an automatic transmission.

  79. Justin,

    2000 Subaru w/245K miles, trans replaced under warranty @ 60K miles, suffers intermittent blown AC/blower fuse under acceleration. AC blows cold, car lurches when fuse blows likely from AC clutch disengaging. Problem started @ ~180K miles and has increased with mileage.

    Had previous diagnostic run, unable to duplicate. Seems to occur more often when car is heavily loaded or when driven more aggressively. Doesn’t seem to occur when only the blower (No AC) is on.

    Transmission does shift somewhat ‘hard,’ especially when starting from park & shifting into reverse, producing a fairly loud ‘clunk.’ Both transmissions (original & replacement) always somewhat balky after first 40K miles.

    Live in California, so AC gets constant use. Possible AC clutch and/or relay or other? Refrigerant level checked and still blows fuse. We keep a box of 15amp fuses and can swap in less than 1 minute once stopped…, but tired of this. Recent 250 mile, 6 fuse weekend trip with heavy load.

    Thanks in advance,


    1. Hi Ken,

      So the Ac fuse blows, but I am not sure why you are telling me about the transmission?

      Has anyone looked at the Ac compressor clutch circuit? That’s the place to start. You could disconnect the AC Compressor electrically and go drive it hard and see if the fuse still blows. If not that kind of tells you that there is something wrong with the circuit that needs to be evaluated, its not going to be a cheap or easy diagnoses and you will need to find someone that will stick with it. If I had to guess the gap of the clutch is to tight.

      The 2000 E4AT transmission was the single worse one Subaru ever built. It may continue to work with symptoms for another 50k or it could become worse next week.


  80. Justin,

    Nice site, I’m hoping you can help point me in the right direction…

    2000 Subaru w/245K miles, trans replaced under warranty @ 60K miles, suffers intermittent blown AC/blower fuse under acceleration. AC blows cold, car lurches when fuse blows likely from AC clutch disengaging. Problem started @ 180K miles and has increased with mileage.

    Had previous diagnostic run, unable to duplicate. Seems to occur more often when car is heavily loaded or when driven more aggressively. Doesn’t seem to occur when only the blower (No AC) is on.

    Transmission does shift somewhat ‘hard,’ especially when starting from park & shifting into reverse, producing a fairly loud ‘clunk.’ Both transmissions always somewhat balky after first 40K miles.

    Live in California, so AC gets constant use. Possible AC clutch and/or relay or other? We keep a box of 15amp fuses and can swap in less than 1 minute once stopped…, but tired of this. Recent 250 mile, 6 fuse weekend trip with heavy load.

    Thanks in advance,


  81. Thanks for the reply Justin. I will bring it in next week and will let you know what the verdict is.

    Appreciate your help!

  82. Greetings,

    I have an A/C issue I am hoping you could help me with.

    In August 2013, the A/C in my 2011 WRX starting working intermittently. The recirculation and A/C light would stay on, however the air would blow cold for 10-30 seconds then compressor would kick off and blow ambient air for 10-30 seconds. It would continue this time cycle. It eventually got worse enough so the A/C would not kick on except 3-4 times during a 20 minute drive.

    The Subaru dealership replaced the A/C relay (Part# 82501AG041) which didn’t help. Then they replaced the thermosensor (Part# 73540FG011) and this fixed the issue.

    Fast forward to yesterday, March 10, 2014. It is getting warmer here in Louisiana, and I am using A/C more often. The issue has appeared to come back. The air will blow cold for 15-20 seconds, and then blow ambient air for 5 seconds. I can only imagine this will get worse just like last time.

    I just got off the phone with the dealership and the part is covered under warranty, but not labor. I don’t want to spend another $600 on another temporary fix.

    Any ideas of why this issue might come back? Think its a defective part or is there another part causing the thermosensor to malfunction?

    Any assistance would be greatly appreciated!

    1. Hi Chad,

      Love New Orleans!

      I am seriously confused as to how a shop does not have to warranty all repairs for a term of at least 12 months or 12,000 miles.

      Your 2011 WRX has a 3 year 36k bumper to Bumper warranty and if you are having an issue with a already repaired item, I would call SOA at 1800 Subaru 3 and state your case. If the car is not already at the Dealer (I wasn’t clear about that) Subaru is going to tell you to take it in, that’s the first step.

      Hopefully Subaru will come through for you and take care of it.


  83. Hello .My 2005 liberty 3 ltrr has a sort of a rattle sound when the compresor kicks in. Can you tell me if this is a easy fix or not.

  84. Hi Justin,

    I have a 2003 Outback 2.5L auto with about 124,000 miles on the clock, and for the last six months or so have had an a/c system that would blow cold when the car was first started but would sometimes then blow hot. If I stopped for a few minutes it would usually blow cold again. Eventually it stopped blowing cold altogether so I took it to a local garage who recharged it and it blew cold for a week or so but now just blows hot air.

    The fans work fine and the clutch engages when the a/c button is pressed. I thought I had a leak so bought some O-rings and a can of sub-zero R-134a but on pressing the low side valve with a screwdriver there seemed to be lots of pressure so I attached the gauge hose of the sub-zero and it read 50+ So now I think that a leak is not my problem.

    I swapped the relay for the fog light relay which is the same spec and that made no difference.

    It seems to me odd that the previous problem was fixed by a recharge but now it no longer blows cold even though there seems to be plenty of gas on the low side. Could the gauge reading be wrong from the sub-zero can and should I try recharging?

    Any other suggestions as to the likely cause?

    Many thanks

    1. Hi Neil,

      I would say the system has a leak, most likely at one of the AC hoses, then you tapped into the system without putting into vacuum for 30 minutes prior to recharging and oiling?


  85. Good Day,
    I love this forum. I have a 2008 legacy sedan. I have been experiencing poor cooling for some months. Each time i refill the gas it works for just a while. I Was told it was a leakage problem. Where else can leakages come from? Checked the engine compartment but found no leakages.

    1. Hello Emeka,

      It has a leak, not sure how you are looking for the leak but there is a analyzer that is designed to sniff out gas leaks., is that what you are using if so the next step is dye in the compressor oil, lastly small leaks can be difficult to diagnose.


  86. Good afternoon,
    I have a 2000 Subaru Outback Wagon with a manual climate control knob (half blue, half red). The A/C worked great until I started using the heat this winter. Every time after switching back from heat, the heat would take over a little bit of the blue side. Now over 90% of the blue half of the control is heat, and only the bottom 10% is A/C.
    When I brought my car in for service the first time the mechanic understood my problem, but didn’t have time to fix it. When I came back a second time, a different mechanic was there that had never heard of my problem.
    Have you heard of this before? Can you tell me the correct terminology to use to get my problem fixed?
    Thank you for your knowledge!

    1. Hello Jennifer,

      Yes the blend door is not working correctly this is what regulates the door in the heater case to control the blend of hot vs fresh or cooled air.

      What has to happen is a diagnoses must be performed to know why this has occurred it could be something is broken or just out of adjustment.


  87. Hi Justin,

    Thanks for responding. Did you have a chance to review the wiring diagram? Am I reading it correctly? Since you are a premier Subaru shop, do you have the ability to discuss this with Subaru tech support to see if they have encountered it? I am really curious about the rational behind the design.


    1. Hello Steve,

      I have not had a chance to review the wiring diagram for your vehicle. There are simply not enough hours in the day.

      Like I had said earlier, I had not seen that before but have replaced the control unit for loss of signal.


  88. I have a 2001 Forester with A/C not working. The bulb in the A/C control panel switch appears to be defective because an ohmeter check shows an open and 12V will not light the bulb. The Alldata wiring diagram shows that the bulb is wired in series with the Evaporation Thermo Switch (which I can’t find and the dealer parts dept couldn’t either) and potentially the Engine Control Module. This suggests “No bulb, No A/C”. Does this make sense? Can a bulb failure truly render the A/C non-functional?

    Interestingly, the bulb is available through the dealer for $12 on a special order with 2-day delivery. This suggests that it is not an obscure failure.

    1. The new bulb measures 50 ohms so I assume it will work. I live in Minnesota so I am waiting for a warmer than 10 degF day to install it. I am still puzzled about a design where if an indicator bulb fails, the system stops working. Anybody have any comments?

  89. Hi all,
    I have a 2000 Subaru Impreza Sportswagon, naturally aspirated. In the US it’s called an Outback.
    I’ve been having an intermittent loss of power for almost a year now. I’ve cleaned injectors, replaced fuel filter, replaced MAF Sensor, replaced aftermarket air filter for stock, checked for vacuum leaks in the engine, replaced Oxygen Sensor (all new OEM parts) and each time the problem returns.
    Sometimes, the problem would present itself when I use the air condition, that’s what lead me to this forum.
    I’m really not sure if it may have some bearing on my particular problem, considering that it occurs generally when the ac is not being used. However, any suggestions on the matter will me appreciated.
    P.S. the Japanese version differs from the US version in several ways but I believe the physics used remains the same.


    1. Hello Bertille,

      I am a little confused with the below.

      “Sometimes, the problem would present itself when I use the air condition, that’s what lead me to this forum.
      I’m really not sure if it may have some bearing on my particular problem, considering that it occurs generally when the ac is not being used. ”

      If it happens both when the ac is on, and when not the Ac wouldn’t really have anything to do with it. Has anyone looked at fuel pressure?


  90. Replaced the compressor, condensor, evaporator, and receiver drier in a 2001 Legacy. AC worked well, system holding pressure, blew cold air for 2 hours in shop. Customer picked up vehicle, AC worked well for first hour, now only blows musty air. Thinking relay or pressure switch…Subaru says they only sell switch with the receiver drier. Any ideas?

    1. Hello Brian,

      What are the pressure readings form the gauges? Is the Ac compressor cycling on? If so what are the readings and for how long, if not where is the power loss? Did it lose its charge if so why? If it still has a charge is AC request showing up on Scan data when the switch is turned on if not why? If so trace down why the compressor is not engaging. Switch, relay, rev sensor, TPS etc.

      I’ve never replaced the switch in question, that doesn’t mean its not at fault I just cant tell you whats wrong with out some information.

      You have some trouble shooting to go do, stick with it I am sure its repairable.


      1. Customer returned today, turns out it was a bad compressor and the clutch is locked up tight. Never had a bad compressor from this supplier, so was a complete surprise. Hopefully we won’t find debris in the system and it has to all be done over again. It was a terrible job!

  91. Air conditioning failed in May on my 2008 Impreza. Vancouver, BC Subaru dealer diagnosed a failed evaporator and replaced it, refrigerant and cabin air filter for over $1100. We don’t use air conditioning a lot in Canada, but by July performance had decreased and by August failed completely again. This time dealer has diagnosed a small hole in condenser, which will cost another $800 – $1000 to replace. How likely is it that we really had both problems within 3 months of each other, as opposed to their just having made the wrong repair the first time? Seems likely to me that the first repair was just a mistake. Would like at least a second opinion. Thank-you.

    1. Hi Randy,

      Its just not possible to give you a factual answer, only to say that typically a hole in the condenser would affect the AC performance the instant it happened and not allow it to work for even one day if present, also rocks and other road debris are typically what take out the condenser. Even a small hole as the condenser is under pressure and pressurized refrigerant leaks out very quickly in most cases.

      It should have ben apparent to you if the evap core was at fault the last time as there should have also been an odor in the cabin when it failed?

      Maybe the Evap core diagnoses was incorrect, and usually when the Tech removes the core its wet with oil.

      Dont know if that helps but thats really all I can offer from here.


  92. The a/c on my 2006 outback seems to work fine while the vehicle is in motion but blows hot when sitting in traffic. I had the system serviced last fall.

  93. 02 wrx the a/c cycles on and off and blows cold then warm air. could this be the thermo sensor or the compressor? the compressor has some brown dust on the back side of the clutch housing?

    1. The dust is compressor clutch material.

      No idea whats the matter with it without seeing it. But in 2002/2003 the Wrx had a known issue with the Thermo-sensor and there is a TSB referring to it.


  94. Hi i have a 02 wrx with the ac pump cycling on and off and blowing cold then warm air i think it mite be the thermo sensor. But there is brown dust on the compressor behind the clutch. could the clutch or the compressor be bad? All so the system has been recharged several times by a mechanic friend and replaced 1 oring on the low pressure side.

  95. ’98 Impreza 2.2 auto. AC was fine, funny smell, like solvent/plastic/ some vapor mist on humid day, then nothing. Garage re-charged and added dye. Worked OK onthe drive home. Sat for a couple days, upon morning start, I turned AC on, sounded like “spray painting inside a coffee can” sound from behind glove box AND that funny smell. I’m suspecting evap coil leak. I have call into garage for advice.

  96. HI,
    What would cause a compressor clutch to disengage while in idle? I turn the car on, turn on the AC, both fans come on, the clutch engages and cold air blows then after a small while the compressor clutch disengages and the air then naturally blows warm. All this is during idle and not driving. I have a 2003 forester.

    1. Hello Damien,

      That sounds like it has a low charge. The Ac system in a car can lose up to 2 ounces of refrigerant a year with out there being a major leak. Because AC maintenance isn’t really covered in the owners manual, most don’t understand that the AC system should be serviced about every two years to avoid low charge and or performance issues. Or it could have developed a small leak regardless of service history.

      To know for sure gauge readings would be required.


      1. A low charge will cause the compressor clutch to disengage and not turn back on again in idle? When the RPMs go up the clutch goes back on. I can tell because I can hear the belt chirp. Both fans are on in idle so air flow over the condensor is not the issue. I actually whitnessed the clutch stop while the car was in idle and both fans were going. It wouldn’t engage again unless I stepped on the gas and brought the RPMs up to about 2K for a few moments. So relays are good, fans are good. What is the proper PSI on the low side when the compressor clutch is engaged? and is there a pressure swtich that could be misreading?

        1. A low charge will cause the system to shut off at any time but so will a faulty sensor, relay or expansion valve etc.

          What I tried to do was give you the most likely, but I cant know whats wrong from here.

          Gauge readings will vary by temperature. With the car off they should be close to even, with the car running and the ac engaged the high side will range from 140 to 200 with a =/- factor of at least 10 lbs and the low side will range from 20 to 40 its when the low side drops down to less than 20 and does so quickly while the high side still has not reached 150 to 200lbs, that you can begin to assume a low charge would be one plausible cause and generally the ac will also possibly disengage when the pressure is low. Its at that time that you would add some R134a and see if the symptom improves. If not that would be ruled out and you would need to look elsewhere.

          Thats all I can offer you from here.


      2. I think My reply got deleted. I asked if a low charge will cause the compressor clutch to dissengage and not come back on at idle. What is the proper low side PSI? is there a pressure swtich that causes the clutch to disengage that could be bad?

  97. Hi Jason,
    I’ve enjoyed your forum. Thanks for sharing your knowledge. I’ll preface my remarks by saying I’m an A/C contractor for residential homes and auto nut. My wife’s 2009 Tribeca has developed a knock/rattle when the compressor kicks in. It is cooling properly. Car has 91K on the odo. Dealer says the clutch is non serviceable.
    Am I correct in thinking it’s time for a compressor? I have all the tools to do the job but not sure besides the drier if other parts should be replaced while it’s apart. Your thoughts….Thanks

    1. Hi Steve,

      Its Justin not Jason thanks.

      If the Compressor failed and debris went through the system than it may need more, if it was just the clutch and the bearing in the compressor did not fail and send debris through the system you are on the right track.


  98. Justin,

    I have a 2002 impreza wrx and the ac is working sporadically. When I start the car in the morning and I instantly turn the ac on it will begin to cool down immediately. After about 10 minutes the air begins to get warm and will not cool down. Had the dealer look at it and they said the freon was a little low and also that the compressor is not compressing. After reading this forum I am sensing it might be something else. They quoted about $1000 for compressor replacement with labor. Thinking about doing it myself looking at the price. Is there another way to know if the compressor is doing it’s job? You have any thoughts??



    1. Hello Curtis,

      If the Charge of R134a (mistakenly called freon) is low there is no way to know the condition of the Compressor.

      the 2002 WRX has an issue with the Thermo-sensor, but I don’t know if that’s what is wrong with your car, just that its a common repair.


  99. On a previous post you mentioned the ac compressor and the defrost being tied together. If this is the issue, then what is the likely cause?

  100. hi justin i have 2001 subaru legacy 2.5 L
    And the problem i have is when i stop at a red light with the a/c on the car starts iddle in weird when is running is normal

    1. Hello Hery,

      As with most 4 cylinder models that have a large cabin area the engine can and will feel much different with the load of the Ac compressor engaging especially at idle.


  101. We have a 2007 Forester 4 with manual AC controls, very basic car. The AC will work fine some of the time and even for extended rides (1-2 hours). It will begin to transition from cold air to hot air other times. The hot air only lasts a couple minutes and then turns cold again. This may happen several times in a span of 20 minutes. This began about two months ago. Suggestions?


    1. Hello Perry,

      I would look at the Charge levels to start with, then at the possibility of a sticking relay. Has the Coolant temp stayed in the normal range the entire time?


  102. I have a 04 Outback with the H6 engine. the air is cold for the first 15 to 20 minutes then turns warm. I have tried the recharge kit, which didn’t help. If the car sits for a half hour the air will be cold then again warm after 15 minutes. Is there a temp sensor that could be bad? I see that this seems to be a common problem.

    1. Hello Chris,

      Common issues would be the Rev sensor @ the compressor or a sticky Expansion valve. The temp sensor in the Evap core could also be at fault, but less common than the other two items I mentioned.


  103. Hello Justin,
    Do you know any reliable shops in Chicago area that specialize in fixing air conditioning systems. I have had a few troubles with my 2003 Subaru Legacy. Parts changed but to no avail, and it gets expensive. When refilled it cools for a couple of weeks but than when I stop driving for a couple of days, the system dries out. I need a real professional to look at it, tired of spending the money.
    Les B.

  104. Hi Justin,
    Are you familiar with the AC system in a ’96 SVX? It was in a “minor” front end collision and, after replacing the condenser,the AC system was checked for leaks and charged. I tested it once on the way home and it seemed to blow cold air. Several days later, when it was very hot, I tried to use it and it cycled on and off rapidly. Each time it cycled on the engine would almost stall (it did once)and the compressor would immediately cycle off. Could this be an overcharged system on a hot day? What do you think it could be?

  105. Hi,

    My girlfriend has a 2003 Subaru Forester that is having A/C issues coupled with engine overheating only on days where the ambient temperature is >90°F,

    The problem presents itself with either freeway or city driving and only when the A/C is on and the outside temperature is >90°F.

    1. The coolant temperature begins to rise significantly above normal but not yet into the red zone.

    2. The air conditioning starts blowing warm air.

    3. The coolant temperatuere starts to fall. Sometimes she turns on the heater full blast to help bring coolant temperature down.

    3. Once the coolant temperature falls close to normal the A/C will again begin blowing cold air.

    Are there any A/C problems that would cause excessive heat generation at the condenser coil?

    I was also wondering if there was any connections between the cooling system the computer and the A/C system. For example if the coolant temperature sensor that sends data to the computer is reading an elevated temperature will the computer turn off the A/C system until the coolant temperature returns back to a lower level?

    Also, as overheating is a big concern to me what is the most likely cause of this overheating situation. Lets assume that the fans, thermostat, water pump, and radiator cap are all functioning properly.

    Does this point to the radiator based on the the fact that it only happens when its hot outside?

    It seems to me that the system only overheats when it is highly stressed. Hot outside + AC Condenser heating up air before it hits the radiator.

    It doesn’t seem like head gasket failure to me due to the specific curcumstances that need to exist for the problem to occur. But, do you think this could be the beginning of that type of situation?

    Let me know what you think and if there are any diagnostics that I should perform to point me in the right direction.

    I have some specialty tools like AC gauges and a multimieter.

    1. You need to address the cooling system, as soon as that gauge starts to move above the spot it sits all day everyday it is overheating, I don’t want to see you damage the car.

      I would read the two head gasket articles I have written on this site. From here I have no idea whats wrong, but you can not continue to use the car until the Cooling system is fixed or it will have blown head gaskets even if it was just a restricted radiator to start out with.


  106. Hi,

    I have a 2007 forester, the ac went out, and I’ve been trying to diagnose the problem to send if its something I can fix. With the ac and fan on high, the ac blows warm air. Compressor clutch never started to turn. Purchased DIY can of coolant and attempted to recharge the system. Pressure gauge read high, in the red…so I took it to an oil change place and had them test it also way into the red from the low pressure side. Not over charged, didnt recharge, so is it air or what? Took it home, check fuses, all ok, jumpered the compressor where the wire harness connects to the battery and the compressor started to turn. Could this be the relay switch, pressure switch, etc? What’s my next step?

    1. Hello Tom,

      Jumping switches and bypassing controls is not a good way to accurately diagnose an issue and you need to use caution. I have witnessed inexperienced individuals do bodily harm working on an ac system and having it vent pressurized refrigerant into there face. this would be the case if the high side pressure cut out switch was bypassed when it actually was correctly not allowing the system to come on as the pressure was too high.

      To diagnose an issue with an ac system you first need gauge readings from both sides, then you need to see if the Ac is being commanded on and not doing so or if thee is no command, then figure out why. There are numerous relays, switches and sensors.

      You should start with purchasing the Factory Subaru service manual if you intend to service the vehicle yourself, not for this occasion but for all occasions now and going forward.

      There is no way I can know whats the matter from here.


  107. AC in my 2003 Forester stops working when I’m idling or driving less than 30 mph. Any recommendations?

    1. Hello Jolanda,

      Most likely it has a low charge brought on by a leak somewhere. If you want it to work properly your going to need to have someone have a look locally to you.


  108. I have a 2003 Forester and this summer the AC has stopped working when I’m idling or driving less than 30 mph. What do you recommend?

  109. I have a 2003 Outback with the 4 cylinder engine. I love the car but my AC has a really weird problem. A few months ago I paid a mechanic to clean the evaporator which he said was full of leaves and dog hair from the previous owner. Every since then the compressor runs all the time unless I turn the fan on, the evaporator freezes up constantly, and the AC won’t cool unless the AC light on the dash is off. I don’t think the thermostat works, the AC is either on or off. I have been putting up with it but it is getting annoying.

    Any ideas. I don’t mind paying for a repair but I am afraid that this will cost a bundle to find the defective part.

    1. Hello Richard,

      With out gauge readings that’s going to be tough to come up with a possible solution. Especially with the ac only working with the switch off part? The rest would let me believe the Expansion valve has an issue


      1. The AC unit cools well when the AC switch is off so I don’t think it is a mechanical or coolant issue. I believe I have either an electrical problem, failed sensor or a bad control. I don’t mind taking it to an AC professional to fix it but I worry that the local “AC Experts” shop will charge me for their rabbit hunt to figure out what is wrong. The closest Subaru dealer is a long drive from here and is rather difficult to do business with. Based on the problem I am experiencing, do you think I need to go to the dealer?

        1. I am confused by this “The AC unit cools well when the AC switch is off”

          Does the compressor turn on and the high side line hot and the low side line cold?

          If the Ac works great when the Ac is off then just leave it off until you can have it looked at.


          1. Justin,

            Yes, everything works backwards. The AC compressor and cooling fans operate all the time the button on the dash is set to off. Basically the logic seems to be:
            Fan and AC switch on – AC compressor is off
            Fan and AC switch off – AC compressor is on
            Fan must on to get the compressor to shut off
            The climate control does not cycle the compressor according to cabin temperature, it is either on or off as described above.

            I have checked the AC relay with a test light. It had 12V on one leg at all times and the ground side is definitely being switched on/off but in the wrong logical direction. It obviously controls the compressor and cooling fan because they cycle with the relay.

            This situation started when I had the evaporator “cleaned” by a mechanic. He said it was full of leaves and dust. He does not take any responsibility for causing the current problem and I have looked under the dash and could not find any obvious wiring issues. I have taken the car to other automotive shops who work on AC units and they really don’t want to work on it. I contacted you just to get a clue of what to do from here.

          2. Where is the mode selector set during all of this is it possible its pointed to defrost?

            If someone removed the Evap core which would be weird as its in the dash and I don’t generally see them fill up with leaves then maybe the thermo-sensor was damaged.

            The car is capable of being diagnosed and very repairable but someone like us will have to do it and it will cost $.


  110. Howdy all!

    Similar issue as many other folks here, 2007 Forester, intermittent AC operation: starts off frosty, goes warm some time afterwards (20-30 minutes?), stays warm for a short time (2-5 minutes?), then cycles back and forth between cold and warm.

    Subaru dealership is, unfortunately, clueless, so I’m taking to the internet streets, looking for a troubleshooting plan. So far, I’m guessing moisture in the coolant could be causing icing in the expansion valve, so a moisture removal process may be in order.

    Any other ideas?

    1. Hello Erik,

      Yes we have seen that issue, its going to either be the expansion valve or thermo sensor at fault. Gauge readings would help pinpoint it.

      Most likely when its blowing warm if you pop the hood and can locate the Expansion valve ( where the AC lines go into the Fire wall) you will observe it iced over. Surprised the Dealer didn’t look for that as that’s actually a common symptom on the Impreza and Forester models.

      Hope that helps and best of luck.


  111. Hey Justin,
    I have a 2004 OBW Base with some AC issues. I replaced a leaky hose, vacuumed down the system and refilled it. It almost immediately started squealing and occasionally making a strange fog horn like noise. I realized that I probably had over filled the system. I removed some of the refridgerent and then it worked great for a month or so.
    Currently, it runs fine at idle, but as soon as you rev it up it starts to squeak. Then the compressor will turn off and on every 2 seconds. If you turn off the car and start it back up, it will work great while idling, and the cycle continues.
    We are hitting the mid 90s for the first time this year, incase that is important to to situation.
    Thanks in advance for all your help.

  112. Hi Justin,
    I’ve just got a 2010 Impreza WRX STI, auto climate control and it seems to control the temperature but the dial has to be set near to max cold to be comfortable, is there any adjustment possible? The cabin sensor has been changed to no effect. Not a big deal normally but if you want to be a bit cooler the dial has to be turned to the max cold position, with the consequential high fan speed and back when cool enough.

      1. Hi, thanks for reply, sorry for delay I have been away. Recirc doesn’t seem to make any difference, but going to the full cold temp setting then it goes to increased air flow at very cold and automatically goes to recirc. It seems to have plenty of cooling ability but it is controlling to a too high temperature? Is there any calibration for the cabin sensor? It seems to function otherwise OK, if cabin is hot it goes to recirc with fast fan and air temp at 2 to 4C as the cabin cools the fan speed slows and then goes from vents to vents and floor at this point if no more cooling is needed the vent air temperature then rises to balance what is required but the temp control at times is one stop from the end! You mensioned Recerc was this as the brain does something different than controlling the air intake, does it change the algorithm? Chris

  113. I have an 03 WRX. Last season my a/c worked lika a champ, yesterday when i turned it on only hot air came out. Investigation reveals that the clutch is not engaging. I have swapped out the relay and checked the fuse under the dash. I have 12vdc at the connection. I tried running a jumper to the back of the compressor and no luck there. Any ideas???

  114. I have a 95 Legacy Outback 2.2 standard, refitted for 134A. Recently the A.C. was being intermittent so I bought some 134A oil charge and added it. The clutch would engage for a second and then quit. In my Chevy truck that means adding more refrigerant until the compressor and clutch engage. I couldn’t add any more refrigerant to the Subaru because it wouldn’t take any. All the pressure was in the hose from the can of 134A. Because the clutch would engage, if only for a second, I want to believe the compressor and clutch are OK, but I have been overcharged where I live for simple things and I am very hesitant to take it back to them. I will go to a different town and have it done, but I want to do all I can to find out if I need to have the comp/clutch replaced, or have it evacuated and recharged. My Chilton’s manual doesn’t really talk about it much preferring taking it to the pros…which I would do if I need to. Any ideas…and thanks in advance for your help.

    1. Hello Patrick,

      Your Chevy Truck uses a low pressure cycling switch to engage and disengage the compressor the Subaru does not.

      It would be my suggestion to Throw the Chilton’s manual in the garbage and buy the factory manual if you intend to perform some of the service yourself. The 1995 Subaru came from the factory with R134a so it could not have been retrofitted, R12 was banned for use in all production vehicles sold in the US by 1994.

      With out gauge readings I have no idea if its low, overcharged, full of moisture etc. From there the Scan data showing the AC request and command cycles from the Engine control module is also needed.

      Sounds like you live in a small town, and that can be frustrating if they dont know the car all that well, it may seem to you that you are being overcharged but may in fact seem fair to them.

      Sorry that I cant offer much there just isn’t a every 1995 Legacy needs this kind of a thing I can suggest.


  115. Hi Justin,
    Just a quick question. Just had air serviced at dealer 2002 Forster. Everything seems to be working fine. But is it normal for both cooling fans to turn on when the air conditioner is turned on?? Another words. Everytime I turn on the air conditioner, The two Fans turn on as well, Even when the engin is cold. Is this normal??

  116. I went to recharge my a/c unit at home, when I tested the PSI on the valve it wasn’t low, but instead it ran higher than the gauge could measure. What would be cause this to happen. It’s a 2005 out a k wagon.

    1. Hi Mike,

      The gauges that come with the DIY kits may not be very accurate.

      The vehicle has a High pressure relief valve so if it was actually pegging the gauge the system would have vented.


  117. Hi Justin
    I’ve sent you 2 replies and do not see them anywhere.
    In regards to the owners manual, yes I have read and do understand how the a/c works. In regards to SOA, already have a case # and they sent there representative out on Thursday to meet and discuss issues.

    I want to make my issue crystal clear. This is not an a/c problem. The problem is, the drivers compartment heats up to VERY warm when the a/c is not on and the temperature outside is 48 to 66. All the dials are in the blue and the fan is off. It gets so warm in the drivers compartment I have no choice to open all the windows and sunroof.

    In aug 2012, I was in 115 degree weather. The a/c was on and the air coming out of vents was cool. The drivers compartment area, as so warm, I had to pull over.

    June 19 2013, the temp outside was 71, a/c was not on. I drove 3 miles and by mile 2, the drivers compartment was so hot, I started to sweat.

    These are some examples of what’s happening. The SOA rep got in the drivers seat, turned on the fan for 2 minutes then turned on the a/c. The air cooled down and that was the end of the dealership run. Both the manager and the r made me feel very stupid, again. I have worked on cars for over 10 yrs, so I do have a basic understanding of how a vehicle works
    Please help

    1. Hello Adrienne,

      I was away at last week and my right arm is currently in a sling, so I am really behind in trying to help some folks out.

      Please understand I can only give general information with out seeing the vehicle, especially with a non typical type issue.

      Does the vehicle have a seat heater? Someone must ascertain where the hot air is coming from if its not the vents?


  118. Hi Justin
    Thank you for responding. I have read the manual on the a/c and how to use. The only reason why I read was becuz I’m burning up.
    I have a case # from SOA. They sent some guy out to meet with me and discuss the problems. He sat in the drivers seat and turned on the ambient air and then the a/c. Of course he said it works fine. Got out of the car and that was the end of the technical part. This must be a new way the technicians are doing thing now.

    I don’t think it’s an a/c problem. I mean I am very warm sitting in the drivers seat in 55 degree weather. It was extremely hot in 115 degree weather too. It was hotter inside than outside. I don’t run the a/c in 48 to 70 degrees. I’ve had passengers in my car and they couldn’t believe how warm it was, as they sat in the passenger seat nice and cool.

    They wrote me back today and told me that the a/c is working fine and they can’t find the problem. “if it happens again, bring it in”.
    This is my second Subaru and I’d this continues, it will be my last. I gave my sister my 2005 at 45k and all of the sudden she needed a new head gasket. Wrong!

    Just so you know, I have worked on cars for over 10 yrs. I do understand the basics and understand when I feel stupid walking away, as if I don’t know what I’m talking about. I’m sorry to blow, but I need some help and this was the only place I found who was addressing a/c.
    Running a/c 24×7 doesnt sound right and recycled air on all the time?

    1. One other thing, the climate control is not the dual auto climate. I have the 3 dials, 1st one on left is where you want to direct the air, 2nd dial is the fan speed and the 3rd is the temp, blue means cold and red means hot…

      The did say its working as it was designed

  119. I have a 2012 forester. I am having a problem with the drivers area warming up to the pint where I want to get out of the car. The weather outside ranges from 48 to 115 when this happens. Last time it happened, I drove maybe 1 block before the drivers area heated up. The temp outside was 61. No butt warmer on and no heat on. All temp dials were in the blue.
    Been to the dealership 2 times and they said I have to ride with the a/c on 24×7 and with the recycle button on all the time. After 10 yrs taking,exhanics, this doesn’t sound right.

    I am tired of these guys looking at me as if I’m stupid. Any comments??

    1. Hello Adrienne,

      Here is what you need to do. start with getting out the owners manual and make sure you are 100% familiar with all of the controls and functions, turning the system off does not mean hot air will cease to flow, its about where the setting was last.

      If after that we have determined there’s no way its not a lack of comprehension of the system we know there is a fault, you will need to go back and be firm , walk in with the owners manual, show them you have read it and explain its not working as designed.

      If after all of this your still not where you want to be the next call is into SOA to complain.

      I can not speak to the staff where you are taking it, and they should never look at you or treat you like your stupid, but having said that we deal with customers on a daily basis that fail to understand an aspect of their Subaru and do in fact take it out on us. Little things like accidentally putting the key less system into Valet mode by messing around with the buttons, hitting the parking light switch on the column, not understanding the climate control and recirculate functions etc. Its just not possible to know on the surface who your dealing with, someone who understands the car and has a real problem, or someone to lazy to break out the owners manual and have a look.

      For a car to be looked at and repaired under warranty Subaru just like every other car company wants to rule out driver error, once that’s been ruled out its up to you to apply the needed pressure to get it resolved, warranty situations can be frustrating for everyone.

      Hope that helps


      1. Thanks for responding Justin
        Answers to your questions| yes, I have taken the manual out and read up because it was so hot in the drivers area. Yes I have called SOA and received a case number and a guy from SOA met me in Santa Monica, ca, yesterday.

        I met with the service manager and the SOA guy. The SOA guy listened to my issue and proceeded to get into the drivers side. He turned on the engine, then the fan. Ran the fan for a couple of minutes and then turned on the a/c. It cooled down as expected. He looked at the dials and then got out, saying its working as it was designed.
        the corporate guy sent me an email recapping my visit to the dealership. Told me if it happens again bring it in. Why, to feel stupid for a 3rd time? O boy.

        The problem is not the a/c. The drivers compartment heats up in any kind of weather, from 48 to 115 degrees outside. Each time, the drivers area was over the temp outside. 115 outside and inside it was coming out hotter with the a/c on and the recylce button on. It happened twice this wed at 330pm and at 7pm, weather outside was 71. I don’t need a/c at sunset . The compartment heated up so much, I almost stopped and got out. I was literally sweating. Happened last week in 55 degrees at 1030pm. I don’t need a/c at 1030pm. The drivers area will heat up whether I go 1/8 mile or 50 miles. It’s almost unbearable.

        As I was leaving, I told them I own several cars, not one has this issue. They just said well this is the way this was designed. I felt stupid, duhh don’t you understand your A/c? They told me to run the a/c all the time and with the recycle button on all the time.

        Question? Is it a safety issue to run recycled air, stale old air , all the time? I get really sleepy and have to roll down the window.

        On a side note, I have worked on cars for over 10 years. I know the basics and understand when im hearing a line of bull. My a/c is the basic model, the one with 3 dials. Nothing fancy.
        Any suggestions? been a loyal customer for over 8 yrs…

  120. Hi Justin, I have a `02` Outback, llbean H6 the compressor clutch will not engage. Gauges show high pressure on high side of system. Fuses and relays are good, have power to the compressor. I just bought the car 6 months ago, in winter, so I have not tried to use the air until now. Any ideas I can try? Thanks for your help. Great forum!

  121. Hi Justin,

    I have a 2008 Subaru Legacy. Sometimes neither the a/c or the heating systems blow at all. Other times they will work fine. I just had my a/c belt changed within 30 days at dealership. I noticed this occurance about 2 days after the belt was changed. Any ideas or advice as to why it will work sometimes and not other times?

    1. Hi Bill,

      Its tough to correlate that from here. The blower motor is in the heater case in the car, and if there is no air flow it may be whats the matter.


  122. Hi,
    I have a 2004 WRX I have a problem with my air conditioner intermittently blowing hot air. It does this when it is about 85 degrees and usually I am going at least 35 mph. I can here a loud thump every time it stops and restarts. I took it to the subaru dealer today and he said the high side pressure is getting over 400 when the gas is pressed, but to do a diagnostic he wants 90 dollars plus the cost of the repair. Is that charge normal? I am a broke collage kid and I really need an air conditioner in south Louisiana.

  123. Hi Justin,

    I have a 2001 WRX turbo. Using my AC gauges, I determined that I had no pressure in the system. I used a leak detector and found both connections on the compressor were leaking. This was probably caused by a repair that Subaru performed. I replaced both o-rings and I am waiting for my AC guy to re-charge the system using his vacuum pump. I am using Johnsons R-134a A/C Refrigerant – 12 oz cans. The shop manual says I need 17.6 oz. This refrigerant does not contain oil. How much oil should be added? The shop manual says “DH-PR”. I think that’s a mis-print.


  124. Hi Justin,

    I have a 2002 Impreza (2.5RS) and the A/C is no longer blowing cool air. The dealership has advised that my A/C pump needs to be replaced. I have looked at an OEM part catalog, and I wanted to confirm that the pump and compressor are the same part. Additionally, they have quoted me about $950+ tax for the service. Is this reasonable, and could this be a potential DIY job?


    1. Hi Chris,

      By law the refrigerant is not supposed to be vented into the atmosphere. So if you have recovery and charge equipment than yes. If you dont than yes it could still be a DIY just know your breaking laws shops cant. You also need to be able to measure the oil going int the Compressor.

  125. hi i have a 2006 legacy. i hear a rattling and a grumbling sound when the ac is on. when i turn the ac off, it continues for 1min and then stops. any help?

    1. Most likely either the tensioner pulley bearing is failing or the compressor clutch or compressor, without someone having a look its all just a guess.


  126. Hey Justin,

    Great info here, so I was wondering if you had any thoughts on my issue before I go to the shop.

    My 2005 92X Aero (WRX in drag) currently has no AC blowing from the vents. There is no noticeable change in RPM to indicate that the compressor is engaging, yet even when the system is off (No AC on), I can hear a whistle from under the hood, at low RPM’s that get higher as the car accelerates.
    Any ideas?
    Thanks in advance

  127. Hi,

    I have a 2010 Outback 2.5 Premium. I noticed recently that the cabin wasn’t getting as cool as it was in the past, and realized that the two left dash vents were blowing out air at a warmer temperature than the two right dash vents. The air on the left side isn’t hot or warm necessarily (maybe ambient temp), but the right side is noticeably cooler (more how AC on a max setting should feel). Any ideas what this might be?

    I should mention too that I have noticed a slight hissing sound coming from the left vents for some time whenever I have the AC running, and goes away when I turn the AC off. I never noticed this in other cars I have had, but thought it was just a whistling sound from air flow. Now I wonder if there is some kind of leak.


  128. I have a 2005 Subaru Legacy 3.0R. Brilliant car however I have just noticed that when I turn the demister on the air blows warm? Everything else seems fine, I just can’t get the demister to blow cold? Why would this be?

    1. Demister?

      If you are letting me know that the air in “any setting” is hot only than there could be an issue with the climate control system that needs to be looked into.


  129. I really love your article above. I recently purchased a 1995 Subaru Legacy. The car is in pretty good condition but the AC really isn’t working. My husband and I work in HVAC so we know our way around compressors, but the compressor and the coil are operating just fine, and it is charged with 134A, it only seems to work when we jump out the relay. When the relay isn’t jumped out the relay turns on and off about every 20-30 seconds. We’re not particularly knowledgeable about car air conditioning so we were considering replacing the relay. Is that a good idea or is there another part we should be looking at that we are not aware of?

    1. It could be the relay, or the switch or something commanding off the AC.

      This is where a scanner capable of data helps as you can see Ac request in the Data stream and also if the computer thinks the Ac is on or off.

      Have you verified signal from the switch to the relay?


  130. Hello. I have a 2008 Subaru Exiga with the right hand side of the AC blowing hot air and the left hand side blowing cold air. I was informed that the O-ring needed to be changed and so it was changed and re-gassed. a few weeks passed and it is back to blowing hot air on the right and cold air on the left.
    what could possibly be the cause and how can it be repaired? is there a possibility that the core needs to be changed?
    May I also add that I really like the info on this site

  131. Hi there — I have a 2004 Outback. The issue I’ve had for a couple of years is: after about 20 minutes of highway driving, no air comes out of the vents. This happens in the summer with the A/C, and in the winter with the heat. I can hear air blowing, but nothing comes out of the vents (it’s as if a door shut somewhere inside the climate control system). If I turn off the system for a while (sometimes for as little as 10 minutes) it will come back on (cool or warm air starts to leak out the vents), or if I stop the car for a while, when I turn it back on, air comes out of the vents.

    I gather that because it takes about 20 minutes of solid highway driving for the issue to manifest, no mechanic I’ve taken it to has been able to replicate it, let alone fix it. Which is why several years later I’m still driving around with the problem.

    Thoughts on what it could be?

  132. I own a 2005 Subaru XT Turbo and my problem with the car’s A/C is that it is making a LOUD noise. It works fine, but that noise is just so annoying. I took it to the dealer and they claim that I need a new blowing fan which is almost $300, but I don’t get it; there is nothing wrong with the air flow. Has anybody have this problem before, and how was it fixed? Thanks.

    1. Hi Millie,

      The bearing in the blower motor may be failing, or it the fan assembly it self may be full of debris?

      It wont work forever making noise.

      Without hearing the noise no one can guide you. $300.00 really isn’t that much money to spend on a 8 year old car.


  133. This site was… how do I say it? Relevant!! Finally I have found something which helped me.
    Appreciate it!

  134. I am working on a 2005 subaru legacy i. The vehicle idles fine until I turn the AC on. When I do turn it on, the rpms drop every time the AC compressor kicks in. I was wondering why it might be doing this

  135. hi justin,
    im working on a 03 outback with a 2.5 manual trans. this is a customers car that i have a/c leaks on for a year+. original issue was the high pressure hose blew, replaced hose, performed evac and recharge. came back, discovered leak at accumulator and condenser, replace all o-rings with oem. came back again still leaking installed new accumulator/dryer. back again, steel line at condenser still leaking and at both lines on the dryer. have u had this issue. i have even tried installing bigger o-rings. leaks out about a month after every repair? im thinking steel lines could be bad or defective dryer as well as condenser?

  136. I took my car in to be looked at and was told that I need a new compressor. I’m saving up the money for it. My question is… now that it is getting cooler out, is it safe to run the heater with a bad compressor?

    1. Hello Karen,

      The Ac compressor should be disconnected electronically by either disconnecting the connector at the Compressor or removing the relay or the fuse.


  137. Hi Justin,

    Thanks for this great forum. I’ve got a 2001 Forester that has the A/C clutch engaged all the time, even with the car off and key out of the ignition. It stays engaged like this until I pull the connector. A/C itself works fine, but there is an obvious electrical issue.

    The clutch being engaged pulls a slow drain on the battery even with the A/C system evacuated, but with the system charged (i.e. full pressure), there is an immediate and complete battery drain.

    I pulled the pressure switch thinking this was the problem and the clutch stays engaged, changed out the A/C relay and it stays engaged. My non-specialized mechanic said it was the control unit shorting out the system, so I replaced that. No change. The only way to disengage the clutch and save my battery is by pulling the compressor connection itself.

    I’m no mechanic, but I’ve gathered that the clutch is getting a 12v charge at all times, which is why it is staying engaged, but any thoughts as to where this short might be coming from if it is not the relay, pressure switch or control unit?

    Thank you!

    1. Hello Jules,

      Not without looking at it, sorry. That’s not something I can arm chair diagnose.

      If I had to guess I would say the coil in the Clutch has shorted to ground. But you haven’t mentioned signal only parts changing and the assumption of signal at all times?

      I would start with verifying the presence of voltage at the connector to the Ac compressor at all times and then trace down the cause of it proves to be true.


  138. I have an 04 wrx, the low side hose was leaking so I replaced it and had it recharged. now i have 12v at the compressor at all times. no matter what the setting is on its engaged, freezes up after 40 mins of driving. so I just unplug the wire to let it defrost. I check fuse, and relay under hood and there is a jumper underneath the relay that jumps 12v to the compressor? I don’t know if it’s supposed to be there? I pulled the jumper out and bought a new relay and it didn’t help just no power to the compressor whiteout that jumper in there. im lost, cause it works great before it starts to freeze up

    1. found that I’m not getting the ground signal to the relay to lock in the relay. jumper is not supposed to be there , so took it out

  139. Hello,

    I have a 2001 Forester. The AC clutch stays engaged at all times, even with ignition off and key removed, so I’m assuming that something is shorted to cause a constant 12v current to the compressor. However, it ONLY drains the battery when the system is charged. Burnt out pressure switch? I already tried changing out the relay, but the clutch does not disengage even with the relay removed. It does disengage when I unplug the compressor itself. How can I determine what is causing the battery drain? Thank you.

  140. Hello,

    Overheating and AC problems. I have a 2002 Outback H6 with 144,000 miles on it. I drove the car around about 10 miles yesterday on surface streets and the freeway here in Los Angeles. For the first three miles or so i had the AC on the whole time and It was working fine, very cold… and i also had NO vehicle overheating issues yet. I then went to lunch and the car sat for about an hour and a half. When i got back into the car and drove off i turned on the AC i noticed it wasnt getting cold and the air smelled a litle old and musty. I was shocked because it was working fine when I parked the car. So i kept the AC off and rolled the windows down a bit to keep cool. I then drove about another 4 miles on the freeway going maybe 50 MPH or so then to the surface streets again…then all of a sudden the car died at a traffic light. I restarted the car in a bit of confusion and anxiety because I was in the lovely and ever so quickly moving LA traffic. Plus the vehicle engine was running so smooth I was perplexed at what had caused it to die all of a sudden. I then glanced at the temperature gauge and almost blew a head gasket myself when I noticed the needle was pegged all the way HOT. The car must have overheated in the last 4 miles because I always continuously check my gauges n things while driving. I pulled over and let the car cool down for an hour or so. When I looked under the car for any water leaks to explain my overheating issue I noticed what appeared to be and was about 3 ounces or so of oil from the AC system. It had leaked out all over the ground. I then determined that my radiator was about one and a half gallons of water/antifreeze low. I added this in water and drove home with no problem. Although upon parking and looking under the car again I noticed water/coolant leaking all over the ground. The next day I found the culprit of the engine overheating issue was a leak/hole in the lower radiator hose. I replaced the hose and flushed the engine with clean water and refilled it with fresh water/antifreeze mixture. The car runs great now and doesn’t overheat. I got lucky I didn’t blow a head gasket. The AC appears to run fine and quiet but it is definately not cold anymore. When I overheated the engine I am assuming I overheated the AC compressor or system as well even though it was off. After reading many of the previous posts my plan of attack for the AC system is to replace the O rings on the high and low side hoses as they meet the compressor. As well as check for any oily residue on the hoses themselves and the crimped areas to determine if a oil/134a freon leak occurred there. Any other suggestions or theories of what to do or why both overheating and AC problems occurred at the same time? Thanx in advance 🙂

  141. Justin
    Just bought a 98 legacy outback 2.5
    The refridgerant was empty, put new seals on pump.
    Evacuated at 29 psi. for 20 min.
    As you add 134 the compressor gets noisy,
    pressures are low 50 high 150
    With more 134…low 70 high 200
    Sucktion and discharge lines warm to hot
    So I tried a used pump and same thing.
    Is there any thing else i need to check before
    I look for a pump at the auto parts store
    I use Napa and O- riely.
    Could it be something else…Dryer,Orfice valve???
    My old haynes AC manual talks about EPR valve, STV/POA
    valve. What do i have?
    New pump is expensive want to make sure its not something else.
    Thanks for any feed back.

    1. Did you add any oil?

      Could be many things, with out seeing it I would just be guessing, and that’s just going to cost you money. The low side pressure of 50lbs with the compressor running is actually to high. When the compressor is off the should be close to equal.

      I would think twice about using anything for the two parts stores you mentioned on your Subaru unless out of a bottle, its quite possible the compressor is defective.


  142. Justin,
    My wife just had her 2005 subaru forester xs in the dealership due to AC problems. It was not blowing cold, just warm air. It was sporatic from time to time that it might try to blow cold. The compressor would spin one time around and then stop for about 5 seconds and then spin once again. this happened over and over when she had the carr in park and the AC on. While driving, if she turned it on, it would “lurch” and not be smooth. The dealer added dye to try and find a leak. They also said that the pulley was bad and replaced that. She had 1200 dollars worth of work done. Now 2 days later, the cars AC compressor supposedly seized and caught fire and melted some plastic under the hood. the dealer now says it was the compressor that was bad and thhat there is no way of telling it was going bad. They want to charge her another 1000 to replace the compressor. They have given her a dealer car to drive and have said that they have knocked off 200 dollars the replacement and will only charge her for one hour or work. Were they in the wrong? Should they have been able to tell if the compressor was going bad? I thought it was just due to the way it would spin, seize, and spin.

    1. Noah,

      When you say she had $1200.00 work done, do you mean in total to the car, or just servicing the Ac the initial visit?

      If it had a 90 k service and front brakes replaced it has no bearing on the fact the AC stopped working.

      We do not see a lot of Ac compressor issues, but it can happen, especially if it had a low charge due to a leak, thus not enough oil to lubricate the compressor.

      Hope that helps


  143. While servicing my AC in my 2002 Outback I found that the heater core is not shut off completly by the mix door, resulting in about 10 degrees higher air conditioned outlet temperature. Is there a cable adjustment that will completely close the mix door? Or is there something not working properly with the mix door?

    I get good cooling normally, and this may have been the way the car was when we purchased it new. However, cooling would be improved if the extra heat from the heater core was not mixed in during really hot summer weather.

  144. Hey Justin,

    I have a 2004 Impreza Outback Sport, you guys replaced the head gaskets and timing belt last november and it’s been running great! About a week ago though, the A/C started to have a strange smell to it, kind of sour and almost “fishy”, as a co-worker of mine described it. Occasional it will also blow out a white mist, usually only when the weather is warmer. Otherwise though, it still works – A/C is cold and heater is hot. I’ve been keeping it off and just cruising with the windows down, while looking online for a DIY solution. I haven’t been able to find anything though, and it sounds like A/C fixes might be a little tricky for DIY anyway.

    Any ideas what might be causing the smell/mist?

    1. Hi Tad,

      That sounds like a Evap core leak if you are getting a fishy smell in the car, dont use the ac until you can have it looked at, the gas is harmful to you.


  145. Justin,

    Great forum posts. I appreciate them. I have a 2003 Subaru Outback H6 LL Bean edition. A/C problems. I couldn’t diagnose it, so I took it to the local Subaru dealer. They said it needed a compressor and speed sensor (in the rear of the compressor). So I bought the speed sensor from them and installed it. Didn’t resolve it. I bought a remanufactured compressor, with a speed sensor installed, and that seemed to work for a while, but problem eventually came back again. In both cases, I evacuated the system, vacuum checked for leaks, and recharged with exactly the right amount of R-134a – 23 oz. checked hi/lo pressure at 1500 rpm – 28psi lo, 245psi hi.

    The new compressor worked great, but only about 90% of the time. When it didn’t work, I could cut the car off, start back up again, and that usually resolved it. A couple days ago, it was really hot – 100 deg. in North Carolina, and while driving down to South Carolina, I couldn’t get the A/C to stay on. I cut the car off about 20 times, but it would run for about 3 minutes and then blow hot again. When it blows cold, it blows ice cold. While reading through forums, it seemed like the issue might be the climate control module. I pulled it to inspect it, and the hose connecting under the dash. After reinstalling it, I noticed that the sensor behind the little circle grille in the front of it, which is in the flow of the air which routes below the dash, was covered with dog hair and dust, from previous owner. I cleaned It off with a pick, and the A/C hasn’t turned on since. Do you think I may need to replace the climate control module? Is the sensor in the front of the module a thermosensor? Thanks.

    1. If you used an Aftermarket Ac compressor that’s most likely the issue.

      It needs to be tested. that way when it fails to work you know the following.

      Does the Ac compressor clutch have a signal to it and fails to engage or does it not have a signal to it and if not where is the signal loss stemming from. With out those answers you are just tossing more money at the potentially wrong repairs. I know that most aftermarket Ac compressors for the 2001 to 2004 H6 will not have the updated speed sensor.


  146. I have a 2007 Subura Legacy wagon, I noticed this week the A/C at first worked intermittenly, and then today did not work at all. Additionally, the temp / radio display can flicker off during the initial start up of the car. Could I have an electrical problem?

      1. the battery was replaced this past winter. I will have the ac re-charged. thanks (it seemed unusual that the ac will run for 10 – 15 minutes after starting the car, then no cold air)

  147. Hello. Lots of great information on this discussion site. I am the owner of a 1992 Subaru SVX. On hot days, the a/c works fine and blows cool air for about half an hour, then it just blows warm air. After stopping the car for a while, that will fix the problem temporarily, but after 5-15 minutes or so the a/c will only blow warm air again.

    Because its extremely hot now, I thought maybe the car was getting too hot and the a/c was shutting off automatically. I got the radiator flushed and put in new coolant, but this hasn’t affected by a/c problem at all.

    Any ideas Justin?

    1. Hi Rick,

      There are so many possibilities its just tough to through out guesses.

      It could still have either a cooling system issue or electrical issue with in the AC, climate controls, or mechanical issue with the Ac such as the Expansion valve.

      The place to start is gauge readings of the high and low side pressures.


  148. Justin

    I have a 2011 Outback 2.5i Premium. The problem is the A/C at idle. I have not taken it in to the dealer yet, wanted to do my homework first.

    The A/C delivers cold air immediately when starting an engine cool enough to trigger the default cold start high engine idle, ~ 1500-1600 rpm.

    The A/C will not deliver cool air upon starting, if the engine has been recently driven (warm engine idle speed ~ 600-700 rpm), until the car has been driven a while. How well the car cools, depends, of course, on the outside temperature, speed achieved and how quickly. The A/C functions very well with the car moving.

    When the car is not moving and the engine is idling, having cool air flow from the A/C vents is unpredictable; sometimes, sometimes not. The following occurs randomly:
    Engine will idle at normal engine idle rpm and there is no cool air flow
    Engine will intermittently rev up and down to maintain a flow of cool air
    Engine rpm will flick up and down very quickly, ~ 1sec, with no A/C output

    Tony Johnson

    1. The Engine is commanded by the ECM to increase Idle speed when the Ac compressor is engaging to prevent stalling due to increased load.

      You cant really correlate a 1 sec blip in Idle speed with air temperature.

      If I had to guess I would say a car wash took out a ambient Temperature sensor.


  149. The AC in my 2006 Outback (4cylinder) operates erratically. It does not cool when the car is stopped but picks up when the car is moving.
    I took it to the dealer who has been trouble shooting. The work so far has cost $750 (included replacement of the expansion valve — they said pressure differential readings led them to think this was needed). This has not fixed the problem so troubleshooting continues. The dealer mechanics say there is some foreign material in the system and the next step is taking apart all of the lines to see if they can locate the source and determine where there might be blockages. This next investigation step is estimated to cost another $350 or so. It is likely some other components will need to be changed out deppending upon what they find, so I am figuring that we will possibly face charges pushing $1200 — $1500 — $2000 — who knows how much.
    I am concerned that I am being taken for a ride here.
    So the questions are these: is there a standard Subaru trouble shooting procedure for these systems? I have asked the mechanics why they have not been able to examine the expansion valve to see from that what the foreign material might be…why rip the system apart further to determine what might be causing blockage — are these not reasonable questions to ask the dealer? I know this is complex — that the number of possible problems is large –but does what I am describing sound within the bounds of reason? Or, should I have them button the AC system up and take it to a mechanic that specializes in AC repair?

    1. Hello Hubert,

      Most Ac issues are straight forward, but sometimes they are not. When faced with a challenge its frustrating for both parties.

      Dont see a lot of Debris or Expansion valve issues, but Debris would ruin even a new Valve so its possible.

      The expansion valve has to be removed to inspect and even then would have to be cut apart to look for any debris.


      1. Thanks, Justin, for your response. It turns out the the final fix, after a significant discount, was nearly $1600.00 (about $520 on parts/$960 on labor). It turned out that there was some kind of obstruction in the receiver/drier.

        The work included, after replacement of the expansion valve that I mentioned last time, disassembly of all lines and components to find the obstruction. It turned out to be a problem with the receiver/drier. As this is rigidly attached to the condenser, the whole assembly had to be replaced. Because it is a sealed component/assembly, the mechanics could not determine what the obstruction was without cutting it apart.

        I would not ask that you spend any more time on this, but, fyi, I have two questions for the dealer and Subaru: 1) design of the component: why did the drier fail in this sealed system? (the drier has a desiccant in it….and I question how it is expected to last lifetime of the car without becoming saturated); and 2) why does the condenser/drier assembly cost $366 when a KOYO Cooling aftermarket condenser/drier assembly costs $122 (a Kool Vue replacement costs even less….$64.63)?

        I question, in general, Subaru’s AC design/reliability. I know they went to a smaller system in the Outback starting in 2005. Also, I will think hard in the future about whether taking the car to the dealer for issues like this is the way to go (rather than bring it to a reputable, independent mechanic).


        1. Hi Hubert,

          The repair you have had to make is not common, the receiver dryer is not a lifetime component by any means its just not popular to tell drivers this.

          As far as pricing anything and everything sold to you by Subaru will have many layers of mark up on it, you will always be able to find a cheaper price on any component available in the aftermarket especially a crash related component like a condenser.

          I don’t like the dealer for repairs, this is because I have an understanding of how things work at a dealership it does not benefit the consumer.


  150. Justin
    I own a 2006 Baja this summer ac has been earatic in performance. did a DIY recharge system was low but minimal. but still have problem. One symptom is a clicking or popping under the dash. When not clicking system works OK. When clicking starts system blows warm air. I was affraid I had overcharged but a friend who has access to a guage set said it is ok. When popping occurs at low speed or RPM I hear a groaning which I assume is the clutch slipping on the pump. Dont notice it at highway speed. Thought maybe cabin filter was extra dirty but even with removed still does same thing. I believe I am up for an expensive fix. Got any sugestions

    1. The Ac relay is under the Hood, so I dont think the clicking you are hearing is from that, maybe the Expansion valve is sticky?

      Gauge readings when its acting up plus possible signal loss is whats needed to know next.


  151. I just bought an 04 subaru outback. Immediately the ac didn’t work. THey charged it with freeon.Then it would work for about 5 min then blow warm air. I have taken it back 2 times since (a total of 3 times now). and each time they tell me it’s fixed and it is not.

    THey have ran a diagnostic and everything checks out. THey said something was leaking and replaced it, and it is still having the same issue. These guys are friends of the family for over 30 years. But I feel they are either unable to tell what is wrong or they DO know what is wrong and realize it will be expensive.

    TEchnically it is still under warantee so they have not been charging me. But I just want my ac fixed.

    It runs fine when it is cold out. When it gets over 80 it only runs for about 5-10 min then it is hot air (or outside temp air) coming through.

    Of course mechanics get pissy if you make suggestions, but I almost want to forward this url to them.

  152. Hi Justin,
    I read through all of the posts and saw one that was similar to mine (Amanda’s), but unfortunately it went unanswered so I figured I’d ask again.

    I have an ’09 Legacy and over the past 2 or 3 weeks I started noticing the A/C was becoming less and less effective (to the point where it really got to blowing cold when the engine was revving pretty high. Late last night it eventually gave out, and today it is still not blowing cold. I don’t think I can hear the compressor running (when I push the A/C button there’s no noticeable change in sound).

    I was thinking today and remember about 3 weeks ago I was on a long road trip and took what amounted to a small “Dukes of Hazzards” style jump over a road crossing that appeared to be missing a stop sign. This resulted in a plastic cover on undercarriage to partially come off (it’s still on, but only being held on by the plugs on the front of it). Does that cover protect the A/C unit? Is it possible that our inadvertent shenanigans punctured the condenser?

    Also, there have been some minor electrical issues recently (keyless entry not working all of the time, windows not rolling up or down until the car is restarted)…not sure if it’s possible that the A/C button is just on the fritz.

    Thanks for your help.

    1. Hi Eric,

      Its possible something happened when jumping the car but I just don’t have anyway of knowing, AC is a system with many possibilities and its just not plausible to be able to know each situation.

      Gauge readings will indicate low pressure, which could be from a low charge and would support that theory, but without gauge readings I am just guessing.


  153. Hey Justin,

    I have a 2004 Outback LL Bean with a leak in at least one of my hoses but am making a trip soon so in the mean time I’m trying to throw some 134a in there but having trouble finding the Low Pressure port. Could you describe or send a link of a picture so i can fill it up.


  154. Justin,
    Read all the posts. Lot’s of good advice here. I have a problem with the A/C on my 2002 Outback H6. I live in Florida and the A/C is an essential component. It sometimes blows cold and sometimes doesn’t. Generally will never start up in the morning first thing. Clutch will not engage the compressor. After shut down and restarting the engine it may or may not start up the compressor next time. No rhyme or reason. It may be the 6th time during the day when it will eventually start and blow cold. After the first time it engages, it will engage and blow cold the rest of the day. After leaving it overnight the problem returns. I think it’s electrical since it blows cold. Took it to my repairman who several years ago replaced the ‘O’ rings and fixed me up when I had a problem with it leaking. Explained it to him. He diagnosed it as a bad sensor that kicks out the compressor when the compressor locks up and that there is a TSB out on it. He ordered the part and replaced it. Did not fix the problem. He admitted his meter was faulty when he diagnosed the problem initially and both parts ohm’ed good (old and new) He says it will take some time to rediagnose it. I decided the climate control unit was bad since eventually it does work although it seems to be getting worse and taking more restarts to engage. I replaced it. Same problem. Any ideas. I know it’s tough to diagnose problems like this online but you seem pretty good at it. Thanks in advance, Ron

    1. Only thing that will actually get to the bottom of it is to be testing for signal loss when it acts up.

      Could be a relay, but could be something else as well.


  155. Hello Justin,
    I have a 2008 Subaru impreza outback sport. Recently I noticed when first turning on and off the defrost I am hearing a “rattling” noise. Seems to be working fine otherwise. My a/c however was just recently used with a heat wave and is making the same noise and blowing warm area. I plan to take it to mechanic this weekend to have a/c tune-up and pressure test. Wondering if you have heard of any similar sound associated with a/c not working. Hoping it is a minor issue. Thank you in advance for your time!

  156. I have a 2005 XT and have had poor AC performance consistently since the car was new. Dealer never found any issue (they just used an IR thermometer in the vent and said it was fine!) even after I dealt with the main office.

    I had my mechanic try his hand it it and he evacuated the system and recharged (just be be sure it was filled to spec) but it didn’t help.

    The deal is this….the AC cycles frequently. I would say it blows pretty cold and feels stronger for about 5 seconds then the compressor seems to cycle off-when it does the air quickly gets noticeably warmer till….about 15 seconds later when it starts over.

    The problem is that even in moderate weather…the car just doesn’t cool down well….in this heat it I just point the vents at me and deal with it…

    I kind of got frustrated and stopped following up on the problem (yes…for a long time!) and I have lived with it but I decided to take another stab at it. in your experience, should I expect better performance than that or is this type of noticeable cycling and temperature change normal?


    1. Hi,

      We also own a 2005 Outback XT, and have no complaints with the AC.

      Not sure whats the issue, only to say its very serviceable. With out temp, pressure and voltage readings there is little I can offer on your exact situation.

      You will need however to seek out a Subaru Expert, or at the very least a competent Technician capable of diagnosing your issue, and willing to invest the time needed to do so.

      What happens is whenever there is an issue such as yours the “market place” does not allow for a proper diagnoses, especially at a Dealership and compounded further if under warranty.

      Sorry I cant offer more


      1. Any chance you could help steer me to someone…(I know that is a long shot….on the other side of the country!) in Northern NJ.

  157. Hello Justin,

    I have a minor issue with a 1998 Subaru Legacy GT limited. The green A/C button is difficult to depress when turning on the A/C. Likewise, when turning it off it sometimes take over 1 minute for the button to pop back out after being depressed. Can some kind of electrical spray resolve this or is the problem deeper than that? The A/C does work fine, but I am concerned that someday the button may simply stay stuck in one position (on or off).


    1. Hello Terry,

      This is actually very common.

      Over time, pop and coffee have spilled from the cup holder into the Climate Control mode selector.

      I would suggest a spray can type glass cleaner like you can purchase at Costco, then spray it on the mode selector and let it sit for a while, it should emulsify some of the residue and free up the button as well as the others. Don’t use Windex or another plastic bottle type cleaner, only something dispensed from aerosol type can will suffice.

      Hope that Helps


  158. Justin,

    Was reading many of these posts and some are similar to mine, but most were not exactly the same. (maybe I just got tired of reading).

    I have a 1996 Subaru Outback 2.2, When idling and driving under 40 mph the AC is warm even Hot, when i reach 45-50 mph it starts getting cold. But is never very cold at all.

    While idling my compressor only kicks on between 3-5 seconds every minute or so. Sometimes only once every 5-10 minutes.

    I tried adding Freon but it didn’t seem to fill unless the compressor was running. I think I only got like 6oz in. Also the pressure gauge on the freon doesn’t seem to be working unless the compressor is running.

    Some people are telling me I just need more freon in there so the compressor can run, is this true or do I have bigger problems with my compressor or other???


    1. Hi Jesse,

      What you are feeling is just cooler ambient air because the car is moving, your Ac most likely does not function.

      The system is going to require much more than 6 ounces to make it work if its empty, and most likely you have a leak that needs to be looked into.

      One of the problems you will run into trying to service your Ac system, is that it is a system, with all sorts of possibilities, most of the time if your freezer quit working you wouldn’t tackle it your self with out knowledge of the system and the proper tooling.

      If the system is so low it blows warm, it most likely was empty, if it was empty is has a leak, if it has a leak you may need test equipment to find it after you fill it.


  159. I have a 2009 Forester. The ac is fully charged and I can hear the ac cycling on and off. No cool air is coming out of the vents.

    1. Hi Ann,

      It could have a low charge, or a climate control issue. Probably bet to have it looked at. If it has less than 36k it may still be under warranty.


  160. I have a 2005 4 banger outback, original owner, baby it. A/C doesn’t blow as cold as it used to, never had the A/C system serviced. I know where the low side ac port is, would it be dangerous to add 134a by myself with an over the counter product w/gauge?

    1. Hi Morgan,

      You can give that a shot your self, however it is a good idea every few years to remove the R134a, pull the system into vacuum , add fresh oil and refrigerant.

      If this is done the Ac compressor will most likely last the life of the car. I would at a minimum add some oil as well as refrigerant.


  161. Hi! I have a 2007 forester. I just got a new alternator. Brake light and battery light came on and mechanic said my charge was at 12?. Anyway, I got the car back today and it stalled twice. I then noticed it is not blowing cold air when the car is idle or in park. It is freezing when the car is moving. The car also feels like it is not getting full power. Any thoughts? Thanks!

    1. Hello Caitlin,

      The 2005 and newer models require a “Memory Tender” to be installed to the OBD port to avoid losing saved data. If this is not done it can stall and exhibit other symptoms whenever the battery is disconnected.

      I can only assume that step was not performed and you may have a vehicle perform erratic until its learned some new data points.


  162. Justin,

    Great to see someone with knowledge and a great attitude.

    2003 Legacy Outback 130K miles.

    AC hoses replaced due to leakage you described. Pressures
    OK, 35 degrees exit air, leaves cleaned out of air supply.

    Blows cold, but thermostat shuts it off and it blows hot.
    Takes a long time to cycle to cold again and the evaporator never gets really cold.

    If I hook up compressor clutch to 12v and drive it, blower on high, it gets nice and cool.

    So I’m guessing the thermosensor is at fault, tho I understand that it could be frosting over. Don’t think
    so with the outlet air so hot.

    How big a deal is it to replace this on this model?

    Thanks, Bill Hale Loveland CO

    1. The Evap core needs to come out after recovering the R134A. This involves dash work as it comes out from inside the car. I would also replace the Expansion valve why you are there.


      1. Justin 2003 Subaru 132K miles
        AC cuts off… thought it might be too much R134
        and the pressure was a bit high — 340# @ 105 degrees: static is about 105# @ 90F. It blows
        cool when it runs. When I jump the compressor
        directly to 12v, it nearly freezes me out. It’s
        NOT the pressure over protection that is at fault.

        What is making it shut down?

        There must be a cutoff based on engine temperature! I finally noticed that when the coolant temp gets above the 3/4 mark–even a little bit–the command to the compressor goes away! And when it’s back above that mark, it
        cools again.

        The coolant temp seems unstable… usually around 2/4 but when it’s hot hovers above and below the 3/4 mark. And it doesn’t correlate much to what’s going on: ie, if the fan comes on, it doesn’t drop. Sometimes it’s highest when just cruising along at 50 mph or so.

        Water pump replaced when the timing belt was
        replaced at 125K miles.

        Relieved to figure out that it’s not the AC at all! But what to investigate first?

        Thanks, Bill Hale

        1. The coolant temperature is way to high if its hitting 3/4 on the gauge if you have owned the car for any length of time you have grown to observe the gauge typically goes a little less than 1/2 way and stays there unto you shut it down.

          Maybe read my head gasket article?


  163. Dear Justin,

    Forgot to mention…re. my ’04 Subaru, system is fully charged…normal pressures…no leaks.

  164. Dear Justin,

    I have an ’04 Outback (2.4)..I have intermittant (25% of the time) interruption of cooling…especially in stop/go traffic (on Long Island Expressway, e.g.). The compressor quits and then comes back on a few minutes later. Seems if I maually turn off AC button when this happens, and wait a few minutes..then push it on, all’s well…until it quits again…often several minutes later.

    I’ve been told it could be a sensor. My mechanic friend pointed to a wired part at the top of what I believe is the receiver-dryer (cannister under hood just in front of PAX firewall). If this is likely culprit, must system be discharged to replace it? What do you think?

    Thanks for great site,


    1. There is a switch in the Receiver Dryer, yes the system has to empty to replace the switch. I don’t think that’s going to be your issue how ever unless someone has confirmed bypassing the pressure switch will resolve it.

      I would suspect a higher than normal compressor clutch gap which can be measured and compared to a range of values, as well as testing for power to the Compressor Clutch when its acting up.

      Hope that helps


      1. Justin,

        Thanks for the tip. My co-worker’s husband is another mechanic (more my age of 66) who saw your tip just now and said I could try direct to clutch power connection and feel if the wire (assuming sufficient guage) gets hot….if so, that’s hi draw and something’s bad. Agree?

          1. Justin,

            Indeed. Okay, here’s the latest: drove home from work w/AC on (AC push button on dash lit) ….after 25 minutes of highway driving…(last 15 minutes in stop/go), cooling stopped….fans at radiator remained on….push button AC still lit…..drove the rest of the way home (25 minutes mostly highway speed) in same mode….no change, no cooling..pulled into driveway…left engine and AC on….inpected under hood…clutch disengaged but fans spinning….pushed AC switch on dash off…waited a second and pushed on….no change Then I pushed AC switch off and waited about 15-20 seconds….pushed back on…voila! clutch engaged….cooling again. Any additional suggestions? (This car has 182K mostly highway miles and is THE BEST)

            Thanks for your help!


          2. Only suggestion is that when it act up it needs to be tested to figure out whats wrong.

            Could be clutch gap, AC relay, one of many switch’s, expansion valve, thermosensor etc.


  165. HI Jason,

    The Subaru dealership wants $453 to replace A/C High Side Line and the O-Rings and adding Freon.
    I was wanting to replace it myself. Is there a forum or a video already on this that you could direct me to that would explain in detail how to replace the A/C High Side, O-Rings, and adding Freon? I’ve found a website that explains adding the Freon. Do I need to evacuate the air and moisture from the system before adding Freon? How does one do that?
    I have a 2002 H6 Subaru Outback.

    1. Hi Dustin,

      I cant direct you to any such forum or post.

      I will tell you it would be a mistake to only replace one hose however, you will end up with a leak sooner rather than later from the other one unless its already been done. Every time we have done one the other has leaked within a year.

      MSRP in our area for both hoses including the O-rings is $389.94 IF you add $25.00 or so for the R134A you will still be ahead if you are capable of making the repairs your self.

      You dont really want to Vent whats left in your system into the Atmosphere. You do need to evacuate the system after the repairs to remove moisture prior to adding the Gas.

      Hope that helps.


  166. 2002 WRX, my a/c has been dead for the past 3 years, after some engine work was done. I finally decided to try to fix it, and it had a leak on the compressor output, replace the o-ring and it seems the leak is fixed. I hooked it up to a vacuum for 15 minutes and it held a vacuum for another 10. So I charged it on the low port to 30psi, turned it on and the compressor engages, but no cold air, and a hissing sound from in the cabin behind the dash while in use only. The high port only measures 90psi in use, and the low port 0psi while in use.

    Is the compressor shot from sitting without use too long? I read that the pressures should be…

    Low pressure: 18-28psi.
    High Pressure: 213-242psi.

    1. Might have a faulty Expansion valve but it could still have a low charge as well, the hissing sound may be pointing to air in the system as a result of the low charge.

      Also the 2003 has a known issue with the thermosensor in the Evap core.


  167. I have a 2012 Subaru Impreza and my A/C compressor turns on and off every 30 seconds or less. As I have never noticed this in any other vehicle I have owned or driven, I feel this shouldn’t be happening. Whenever it turns on it makes a loud click/hissing noise, which is accompanied by a loss of power to the engine and a slight accelerator movement at my foot. I can sometimes hear the noise when I have music playing, but usually have my music loud so I don’t have to deal with the noise. I went to Subaru to discuss this and they say its normal, but why would a brand new 2012 car do that? It gets really annoying on long drives, which I do quite a bit. Suggestions/Thoughts?

    1. You could potentially have an aggressive compressor clutch gap causing the noise, in which case the fix would be to use it. But you haven’t really described anything unusual.

      Have you tried putting your mind at ease by driving another one?


      1. Yes the aggressive clutch gap sounds like a possibility, because the sound is quite an aggressive noise. What do you mean the fix would be to use it? As in the more I use the A/C the quieter the sound will get or will the sound/feeling just go away from use?

        I have tried driving another one, it made the sound, but it wasn’t as aggressive.
        I just find it odd that a brand new car makes that noise, while my old 2001 Nissan Sentra never made the noise, or consistent loss of power, 1999 Ford Taurus didn’t, and I can list a few more that didn’t have the same noise or reoccurring power loss sensation. Its unsettling knowing I will have to deal with a “bumpy” ride in a brand new car that I spent quite a bit of money on for a car with a supposed comfortable ride.
        I don’t mean to come across as complaining, but I thought if I spend 30k in our times (2012) that I would get a product that drives comfortably and doesn’t have an A/C compressor that turns on and off every 20-30 seconds, reducing power, and making an aggressive annoying sound, and now allowing me to fully enjoy my Subaru as I had hoped.

        1. Greg,

          I have never observed a 4 cylinder car that did not lose power when the AC engaged, The 2001 Sentra you mentioned did that, I know, I worked at a Nissan-Subaru Dealer as a Technician for years I know the 2001 Sentra as well as I know the 2001 Outback. You must have owned the only one that didnt. The power sensation will be more prevalent on a AWD vehicle than a 2wd vehicle and the load that’s already on the engine will dictate the power loss when the load is increased when the AC kicks in

          The Ford Taurus most likely had the 3.0 or 3.8 l 6 cylinder and is hardly a comparison.

          The ac engages based on pressure and temperature and disengages for the same reason, when a pressure value is met.

          Not sure how the ac coming on is causing a bumpy ride.

          If you think there is truly something the matter with your 2012 Impreza you need to contact SOA if you didn’t get any where with the Dealer. Ask for a Rep to meet you at the Dealership, show him your concern, let Subaru tell you if its normal , compare a few cars.

          Did it do this on the test drive before you bought it? If no when did it start and you need to communicate that to Subaru the day it started, if yes why did you buy it? Regardless, this is the first I have heard of this, we have serviced several, my In laws own one as does a very close family friend I have spent a lot of time going over the 2012 Impreza as it had a lot of new technology and I wanted to stay current, I have again not experienced anything so radical on any of the 2012 Subaru Imprezas I have driven.


          1. Yes, your right. Both cars, and all do lose power once the A/C is turned on, just this vehicle is the first where I feel it cycle every 20 seconds. During the test drive I never really paid attention to see how the A/C effects the drive, because I never thought it would do so as much as it does.
            I wouldn’t say its a bumpy ride, but I would say the sensation is one of a person shifting gears in a standard vehicle every 20 seconds. (I timed it)
            I have had a few friends drive with me, and drive the car and they say they have never felt a car do that every 20 seconds, only on the initial turning on of the A/C.
            I have a check up scheduled this week so hopefully they can give me a proper answer for this situation, and if not, I will follow up with SOA and see what can be done.
            Thank you for your help and advice.

          2. Justin,
            I have a 2013 Forrester Manual 4 cyl. I am experiencing the same thing. I think there maybe some miscommunication. Whereas, it is normal to have a loss of power when the a/c turns on this is different. Instantaneously there is a pop hiss air blow off noise with a quick jerk loss of power that feels like you hit a bump. It does it during acceleration, breaking, coasting, clutch in and clutch out. It did not do it during the test drive and only does it running the air. I have gone to the dealer and they say they can’t feel anything and computer diagnostic is normal. It was suggested no kidding “well little lady this is a manual and you just might not know how to drive it aggressively enough”. Even though no one died from that comment I did point out that I drove valet for 3 years, have driven manuals my whole life. I digress. Sorry. Any tips?

          3. Hi Johanna,

            With out seeing it here and experiencing the issue you are describing there is unfortunately little I can offer, Id stick with it how ever as it does truly seem like there is an issue, you may also want to call SOA 1 800 Subaru 3 and have a chat about your concerns. If you can make it act up request a tech goes for a ride with you…

            Hope that helps


      2. And I understand there is power loss whenever you turn the A/C on, which I did experience in my other vehicles, but not as a reoccurring cycle every 30 seconds, which I experience in my ’12 Subaru Impreza.

    2. OMG Greg. I bought a 2012 Impreza in May just three months ago and I have the same issue and am told the same thing. There is nothing wrong with the car. It is so annoying on long trips like you state because of the loss of power. To make it worse I bought a stick shift so when I lose power as I am shifting the car bucks back and forth for a second or two. That is even more annoying. Glad to see I am not alone and I am definitely going to pursue this further seeing that someone else is having the same issue.

      1. I have the SAME problem in my 2012 Impreza, and was told it was normal. It is really annoying. Now that it is getting colder, and I have to use the heat, I notice the SAME thing (which I dont understand since I’m not using the AC)That loud air wooshing sound and loss of power is the worst!

  168. This forum is amazing. I have a 1997 legacy L wagon, 2.2L. I need to replace my AC compressor and clutch. I have three questions: 1) Used compressor/clutch with warranty – do smart people take risks with used compressors? 2) Do the 2.2L legacies share similar AC components with 2.5L Outbacks and GTs? (for swapping purposes) and 3) Do you do any paid phone consultations for some unrelated subaru performance questions? I’m in California. Thanks!

  169. Hi Justin (great name!),
    My ’08 Impreza 2.5i has had some A/C problems for a few years. While it was still under the intial service plan I had with my dealer, I would have it re-charged every six months, or so, and things would work. They told me one of the hoses had a slow leak. Now, a year after the plan and the vehicle’s warranty have expired, I took it into my mechanic to have it re-charged again, but now the leak is much worse. They changed the hose, but the A/C kept blowing hot air. After taking the car back, they’re telling me that the Evap core is also leaking, and that the work + part to repair it will be around $900. At this point, am I better off taking it back to the dealer to have this work done? My mechanic can’t believe that a four year old car is having this issue, is it uncommon and I just have terrible luck? Thanks, I’ve enjoyed reading your comments!

    1. Hi Justin,

      Yes it is a great name and if you are under 40 you were named after me!

      It should have been repaired under the service contract, its very unfortunate they just kept adding more R134a.

      The Evap core is not a common leak, but we do see a few.

      If you have repair orders from the Dealership showing the constant refills and no fix you should call SOA, and have a conversation about a warranty repair not being handled correctly, they may even go back and audit the Dealership to see how much they were billed to not correct the issue. I think you have several arguments to make and should hopefully get some help.

      I imagine you must live in a smaller market? I just cant imagine a large Subaru dealership pulling anything like you have mapped out.


      1. Thanks for the quick response!
        I’m in Northern Virginia.
        The entire time the dealer serviced it, the Evap core was never even mentioned. My mechanic missed it twice, thinking the hose was the main problem. What recourse could I have if my dealer claims the Evap core wasn’t leaking during the time period they worked on it?

        1. Im confused now.

          Did you take it to the dealer every 6 months and all they did is add more R134a? If you had to take your Subaru back o the Subaru Dealer every 6 months because the AC system was low, and there was never a documented repair for a leak Subaru would not like that very much. When I worked at a Dealer there was seldom any Warranty pay issued unless there was a defective part replaced, you could site one time the system was low, but if it was found to be low 6 months later there had better have been a repair documented before a AC service was billed to Subaru. If the Dealer was Good willing the top off every 6 months then you need to ask them why they never attempted to permanently repair it? If you have documentation the Dealer was topping it off that would be good enough I think.

          Now if you took it somewhere else to have the Ac recharged other then the Subaru Dealer there would be no record, and yes you would be on your own. You should not have paid to have someone recharge it while it was under warranty, and if a independent shop notices an issue its up to you to make an appointment to get it resolved.

          If the car came to my shop at say 30,000 miles and the Ac did not function as it should we would have inspected the condensor for rock damage (just behind the grille) if its damaged and leaking we would have given you a estimate to repair it (as a damaged condensor is not covered under any warranty), if the condensor was not leaking because a rock or the like had come in through the grille and caused a leak, we would not have performed any service to it, we would have instead informed you that your Car was still covered under Warranty.

          Hope that helps


          1. Thanks, sorry for confusing you. The A/C started acting up right at the end of my service plan/warranty. At a scheduled maintanence, I asked them to take a look at the A/C and they recharged it. Two services later (ironically the last that was covered by my plan), they did it again when it began to blow hot air. The service in between was during the dead of winter, when I hadn’t used the A/C in quite some time. It actually worked all of last summer after that second re-charge. Once it started getting warmer this spring, it wasn’t working when I began wanting to use it again, and that’s when I took it to my independent shop mechanic and got my current diagnosis.
            I’m guessing my dealer would have records of the services they performed? I think I have my copies, but not sure if I have them all.

  170. So I have a 02 wrx just recently my AC stopped working. Compressor and clutch are working but the system isn’t getting cold, I checked my levels and I’m still charged. The only thing I’m hearing is a hissing noise coming from inside the the car any thoughts on what I need to do to repair or fix my system?

  171. Hi Justin

    I’d 1st want to say thank you for all the responses. You are very knowledgeable and courteous in replying to all the questions.

    I have a 2008 Impreza and when I turn on the A/C it works then after a few minutes (even though it is still “on”) there would be no cold air. I’ve had it diagonosed by a dealership and examined by a trusted mechanic. Neither were able to find a problem. The fre-on was re-filled which made the system less prone to this “on/off” scenario. But it still occurs.

    Have you experienced anything like this or know what I should tell my machanic to look at?
    I’ve love to take my car to you, but I’m not in the Seattle area (actually I’m in Toronto).

    1. Hi Henry,

      Yes we have seem that issue but the fix was different each time, I dont have enough information at this time to be of much help. It could be an electrical issue, a blend door issue or a mechanical issue with in the Ac system it self. If it didn’t act up for the shop when you had it in it would be hard to determine the cause, but if it did act up im not sure why it couldn’t be diagnosed?

      Does it act up all the time every day or is it more intermittent than that?


      1. Thank you for the response.
        It does act up daily. I’ll have the ac running then I can feel the compressor turn off (you can hear/feel the change in the engine). I was wondering if there’s a solenoid that would engage and disengage the ac?

  172. Just as an FYI. For almost a entire summer my 2004 subaru forester was having intermittent a/c issues. It would blow cold air when I first started the car with a cold engine but as the engine began to get hot after driving for a while it would start blowing hot air out the vents. The problem steadily get worse as the outside temperatures got hotter through the summer. I tried charging the system but that didn’t work. I looked to see if the a/c clutch was engaging and it appeared to be but I couldn’t really look when it was blowing hot air as it usually happened while I was driving. Then I bought a set of manifold gauges to make sure the system was indeed properly charged and that the clutch was cycling on and off at the proper pressures. Again it appeared to be working correctly but it was hard to tell because I couldn’t check it when it actually blew hot air out the vents. I checked the a/c clutch air gap which was at the outer limits of the specification but still within spec. I checked the a/c relay for proper function and it too was working fine. I then ran a jumper wire from the positive battery terminal to the a/c clutch electrical connector and took the car out for a drive that usually would have caused it to blow hot air and the vents blew cool air the whole ride. This helped me narrow the problem to the a/c clutch itself but I checked for voltage drops in the a/c clutch circuit and was unable to find any significant drop. At this point I was sure the clutch itself needed replacing but I was unable to find a replacement clutch for sale. Subaru itself recommended replacement of the entire compressor if the clutch didn’t work properly or even if the clutch air gap was too large. Paying $400-500 for a new compressor and paying someone to evacuate the system so I could replace the compressor was not really an option financially so I kept looking for other solutions to the problem. Eventually I found a thread on a subaru forum saying that there is actually 2 shims between the end of the shaft the clutch is splined to and the a/c clutch itself and that 1 or both of these shims could be removed to decrease the size of the air gap. The reasoning behind the need for this was that in hotter weather the extreme underhood temps decreased the strength of the magnetic field created by the electromagnet in the a/c clutch preventing it from being able to close the larger air gap and properly engage the a/c compressor pulley. This seemed to make sense and since it would be pretty much free, I decided to give it a try. After attempting to rent/borrow an a/c clutch puller I found the ones at autozone and advance auto did not work on my subaru’s a/c compressor and although pep boys had the proper tool it was already rented out at both my local pep boys. I wound up making my own puller which actually worked quite well and after getting the a/c clutch off I initially removed both shims and replaced the clutch. This turned out to close the gap too much and once the clutch had engaged would no longer disengage to cycle the a/c on and off properly, although by my measurement the air gap was just below the lower limit of the spec. Once it had been engaged it wouldn’t disengage until I either turned off the car or disconnected the clutch electrical connector. At this point I removed the a/c clutch again and replaced the thicker of the two shims and reinstalled the clutch again. I then measured the clutch air gap and it fell right in the middle of the specification and I have not had a single a/c problem in the 3 years since. Just thought I would offer that knowledge up to anyone having similar problems with their subarus a/c functioning intermittently in hot weather.

    1. Compressor Clutch gap is something an experienced Tech should look at if the determination was there was a signal to the Clutch but no engagement or it wont disengage either..

      Its good you were able to avoid the Compressor expense.


  173. I am trying to help my son out with the air conditioning on his 2002 outback. I noticed the clutch was not engaging. I traced it back as far as I could. There is power at the relay and when I jump it to B+ the clutch enables. He was going to have it serviced but I figured we would try and fix this before he took it in for leak testing and save a couple of hundred bucks on diagnostic time. I cant find a wiring diagram anywhere and I do not know what else would dis engage the clutch. The fuse is good. I am guessing there is a temperature or pressure switch somewhere to check. Any ideas?

    1. The wiring diagram is in the Service manual.

      You will need to determine source of voltage loss to the Clutch, there are to many possibilities to go over each one with you in this forum..


  174. Your article states: The 2001 to 2004 Outback with the H6 has some of the same leaky hose issues that plague the 4cylinder models.

    I own a 2002 Subaru Outback that’s experiencing air conditioning problems. Since this seems to be common knowledge, was there a recall? The dealer is quoting $375.00 to repair.

    1. Hi Jennifer,

      Recalls are typically about Safety items, and lets face it non functioning Ac while inconvenient, is far from a safety issue.

      Most makes and models will need some ac service after 5 years, $375.00 is not a lot of money to have to spend after 10 years of service out of the AC system.

      Hope that helps


  175. I have a 2000 Subaru Outback with 194k miles on it that my wife drives. Not knowing anything about AC and the need for maintenance every 4 yrs, I never did anything with it (bought the car at 112k miles). Recently, the AC decided to quit.
    I put the dye in the system and found where it was leaking and since the one O Ring had gone bad, I just replaced all of them, and then filled with refrigerant. It held, but blew hot. The manifold gauges read low 40/high 50. I did some research on the net and it said that the compressor was likely bad. I ordered a used compressor online (90 day warranty) and installed it. A friend loaned me a Harbor Freight vacuum pump and I sucked the system down for about 15 minutes, then filled with refrigerant. This time the low side showed 40 and the high side showed about 45. The clutch on the compressor engages but it still blows hot, and from what I’ve read the pressure needs to be around 150 or more on the high side. Outside temperature was about 75 degrees at the time. I let the AC run for about three minutes and checked the pressures again, and this time the low side had dropped to about 35. I also heard a low hum/hiss from inside the car coming from the vents.
    Bottom line: my pregnant wife is still driving around in a hot car. Any ideas? After reading your post and several other things on the internet I’m not as concerned about the low side dropping as the car was on and it seems like that may be normal, but my high side is definitely wrong. From my internet research it appears that this car uses an expansion valve rather than an orifice tube, and I can pull it apart and check to see if that is bad (I’m assuming its behind my dash?) and maybe the evaporator is leaky? Any help would be appreciated.

    1. Jason,

      It may have a low charge still, or wasn’t held in vacuum long enough. A good test is after an evac of 15 minutes how long did it hold -15 inches of mercury?

      Also not sure how accurate the gauges are, are you?

      Id add a little more and see how it goes


  176. I have been having problems with the AC in my 2008 Tribeca for over a year now. Fortunately (or unfortunately depending on how you look at it) living here in the PAC NW I don’t use the AC very much, so the problem may have existed for much longer. I took it in to the dealer last August and was told that coolant was empty, it was recharged and worked for the rest of the time I needed it – probably a week. This spring, again it wasn’t working (not blowing cold air), so I took it back in. I was told that the suction fitting at the compressor was leaking. The hose/o ring assembly was replaced and the system was recharged. Again it worked when I picked the vehicle up from the shop, but the next time I tried to use the AC (about a week later) it wouldn’t get cold. I returned it to the dealer and this time I was told that the problem was an intermittent power relay, which was then replaced. The AC worked when I picked the vehicle up (yesterday), but today, again, stopped getting cold and now only blows warm air. I purchased the vehicle in another state before moving to my current location and it is being serviced under the extended warranty plan. How likely is it that the service department isn’t trying very hard because I purchased the vehicle in another state and the work is being performed under the extended warranty plan? Am I just getting the run around? Thanks for your help.

    1. Hi Lee,

      Ac is actually the single most frustrating system to diagnose sometimes. You can have a small leak that is very difficult to determine the cause or multiple slow leaks that show up one at a time, an electrical issue with the automatic climate control system and than the market place just doesn’t allow for proper time for a proper diagnoses with everyone trying to perform Ac services and the average driver not understanding all of the complexities. Then yes, when you add a warranty company to the mix it can add a entirely different element to the diagnoses in the way of who is paying for it. It doesn’t sound to me like that’s exactly whats going on in your situation but with Jiffy lube offering cheap ac services, it has made it very difficult as a shop to get paid to properly diagnose a problem, when there is one that is not straight forward.

      I am not aware of any typical issues with the Tribeca which is most likely why its been such a back and forth situation for you. I would make arrangements with the Service department and state you “don’t want it back until its perfect”.

      I hope that helps, and It can be fixed.


  177. I have a 2001 Outback Legacy wagon, base model, 4 cylinder with automatic trans, manual cabin temp controls, 168,000 miles. I am original owner. Never had any AC problems until now. No AC preventative service has ever been done, not even a can of AC gas added. It will not get cold, I don’t think the compressor is coming on at all. Blower is fine, blows at all speeds selected. I have noticed that it sometimes will suddenly get cold if I have been driving a while and when that happens I hear a noise like a water draining through a pipe. It comes from the cabin right front footwell, which I guess is where the coils are that the air blows across. It did this just a few times, but seems to have stopped completely from getting cold.

    I also had a 1985 Subara DL sedan from new until 1993. I remember the AC on this stopped blowing cold suddenly several times and the fix was always to have an electrical relay replaced. Probably happened at least 3 times in 8 years. I have been trying to find if there is a relay on my 2001 for the AC but all I can find is the fuse in the cabin fuse array, which is fine.

    I am tempted to just add a can of refrigerant to see if it is just low pressure after 11+ years. I used to do this with my dad in the driveway way back. If that doesn’t work I will probably just take it to a dealer. I plan to keep the car for while longer for teenage drivers.

    Thanks for all your posts.


    1. An Ac service really should be done every couple of years, if its not working now its most likely low or empty due to a leak.

      You can try adding a can of R134a your self, but if its short lived and you dont have the test equipment, or the ability to diagnose why its not working, its probably better to let someone else have a look. I will add the venting or leaking out R134a is not a good thing.


      1. Still working on the 2001 Legacy Outback wagon. I bought a can of R134A that came with a simple low-side pressure gauge. It showed no pressure and took the whole 18 ounce can. That brought up the pressure but not into the “green” on the gauge (adjustable for ambient outside air temp) about 20 PSI if I remember right on a 75 degree day. The compressor kicked in after the pressure rose and it started blowing cold. It was not always blowing cold, so I added another 12 ounce can of R134A, which still did not bring the pressure all the way into the green. It was blowing cold more often, but still takes about 10 minutes to get cold, stays cold for about 10-15 minutes then starts blowing warm again. I pulled the relay and it checked good for continuity both with and without 12V. I haven’t seen anyone talk about that, found that in a Subaru tech manual on a CD I bought several years ago off of ebay.

        Do you think this might be an “air in the line” problem? I don’t want to add anymore R134A. I am about to finally give in and take it to a shop.

        Thanks for your help.


        1. If it works when you add more R134a its not going to be anything electrical such as a relay or a switch.

          You most likely have a leak, that needs to be repaired than an ac service performed. Unless you posses the proper leak detection equipment you will not be able to find most refrigeration leaks.


          1. Hey when my 02 legacy wagon is runningit makes this really loud roaring noise. It sounds like its comimg from the A/C unit underneath the hood. Any Idea what this could be? It gets louder when I accecerate or rev the engine when in park. It does it whether the AC is on or off. I’m like 95% sure its coming from the AC unit under the hood. The part that the belt connects to is where its loudest at

          2. Hi Jon,

            I cant really comment about a noise I cant hear?

            You can take one belt off at a time to see if the noise goes away as a diagnostic tool.

            Hope that helps


  178. The air conditioner on my 2004 Legacy 35th Anniversary Wagon did not cool well when it was over 80 degrees, for 5 years. The repair guy couldn’t find a problem, system had the right pressure. He suggested he could try adding a half-can of refrigerant, which he did, and it has worked well on the hottest days since (now April, 2012).

  179. I have a 2008 Subaru Legacy 2.5, the a/c nor the heating systems blow any at all. Is this a fan issue or something more serious?

    1. It could be the blower motor/ fan or just a blown fuse plus many other things as well.

      Its difficult to speculate without information like there is power to the motor but it fails to come on, or there is power but no ground signal. Anotherwords you or someone esle will need to delve into whats the cause of the malfunction.

      Sorry I cant offer more.


  180. I have been a Subaru owner for few years now. Bought my first 2000 Outback in 2002 and just recently traded it and got a 2004 Outback and i am having weird A/C issues in the 2004.

    The A/C works fine most of the time but on long drives (30 + mins), making no changes to the vent settings or anything, the vents in the system all close. So one mintue with the A/C on full blast I have cold blowing air coming out of my main vents (the 4 accross the front of the car) and the next there is no air coming out of any vents BUT I can still hear the system blowing like crazy it’s just blowing in my dash. When it does this, if i press the A/C and turn off the A/C after about a minute or 2 the systems corrects itself it blows correctly but it is still a reoccurring problem.

    I have taken it to the guy i bought the car from and have even made a video showing what happens and he is very willing to help but he needs to see it happen and of course I can’t make it happen when i need it to happen.

    I am assuming it’s some sort of vacuum issue. have you ever seen this? If so how do i need to direct someone to fix it?

    1. Hello Michael,

      You didn’t let me know if its a 2004 Subaru Outback 4 cylinder or 6 cylinder and whether or not it has manual or Automatic climate control.

      Regardless its not a vacuum issue, its a mode control issue that will need to be diagnosed. If the mode selector is on AC and dash vents and it works and then doesn’t there is an intermittent problem with either the mode selector, Body Control Module, climate control module, mode door actuator, wiring etc.

      There isn’t anything I can offer you except to say its very repairable, not a common issue and will need a qualified Subaru Technician to get to the bottom of.


      1. I’m not a pro but I can tell you that this is exactly the symptom from the Evap ‘freeze-up” in my 2003 WRX, a symptom which is more common in high humidity conditions (and temporary cure is to turn the heat on full for a couple of minutes.) I was charged $150 for a check & top off refrigerant at the dealer who DID NOT notify me about the sensor TSB which was issued for 01-02 built cars.

        1. Hi Jon,

          So there are many things that can affect the AC some intermittently some constantly until resolved. The TSB for the Impreza does not apply it uses different components.

          I am not sure I understand your complaint though did you still have an issue after the AC service was done that led to having the thermosensor relocated? The TSB wasn’t a free thing for many WRX owners by the way, it was a TSB not a recall. Meaning the purpose is to cut down on Technician times to diagnose a problem by making the problem and resolution of the available.


          1. Thermosensor was never replaced, too expensive to consider, just corroborating symptoms on different vehicle of vintage near the TSB’d models. This vehicle later had to have the compressor replaced because its bearings went bad although it was still working. Now, after