2005 Subaru Outback air conditioning problem

I bought this car about 5 months ago, with 37,000 miles on it. Now that it has gotten warm, I’m noticing an intermittent problem. The AC will work fine for a while, then stop working. My mechanic found that the low side pressure stays fairly constant, while the high side pressure will bounce around considerably and get very high (up to 500 psi). They flushed the system and the problem got worse. The AC will work on part of a short trip, then stop. On the return trip, it may or may not work at all. My mechanics are stumped. They think it may be a switch, but they’re hesitant to put one in, have me drop $150, and then have it not solve the issue.

What switch do they think might be causing this problem?

They’re not sure at this point. They don’t want to put one in ($108 + labor for the high side sensor/switch), if it isn’t the correct one.

Since the system was flushed and the problem has gotten worse I would suspect something is still inside the line causing the trouble but that is just a guess on my part.

How can they quote a price and not know which switch they’re talking about?

It was $108 for the high side switch (as I mentioned above). But, they don’t want to just start replacing parts without some assurance that it’s the actual problem.

What motivated a system flush? this usually happens after a compressor comes apart, did your compressor explode (internally)?

Does having a large fan blow on the condensor bring the high side down? Are you electric fans working correctly (not just moving but moving at the right speed)?

When they tested the system, they were found the strange pressure fluctuations (I don’t remember these exactly, even though I was watching). The fans appear to work correctly, although I don’t know that they tested these. They did spray water on the condenser when the pressure was increasing, but it didn’t make any difference. They thought that some air may have been trapped in the system, thus the flush. They’re now trying to investigate possibilities, while I’m doing my own research.

What I experience, such as two recent short drives, is that the AC worked fine for the first 10 minute drive. When I started the second drive, it worked for about 5 minutes, then alternately put out heat and cold, then finally stopped putting out any cold at all. When it’s not putting out cold, it sounds like it’s trying to start (a quieter engine type roar for about 1 to 2 seconds, followed by a 5 to 10 second gap, the repeat).

This link should help explain.

Scroll down to “Pressure regulating Devices”.

I have the very same problem with a 2001 Outback. I took it in for routine AC service and now I need to take it back since the problem isn’t fixed. Have you learned anymore about what is causing this?

Well, as it turned out, it was a kind of non-problem. My mechanics refrigerant machine was not calibrated correctly. The Subaru dealer found that it was overcharged by 0.5 pounds. It’s worked fine since then. Great for me, but I’m not sure this is your problem.

My 2008 outback has similar problem. The AC works for 45 minutes then the vents stop flowing air. If I stop for five minutes or switch the AC off for five minutes the AC and vents work again. I think the core is freezing over and blocking the vents. When you stop the AC the ice melts and opens the vents. There must be a sensor that switches off the AC so that the core defrosts. I had a dehumidifier that had the same problem. I am going to the dealer to get it fixed on warranty on Monday. Does anyone have a similar problem and did the dealer fix it?

I have a 2005 Outback with a similar problem. The ac just stops cooling sometimes. The dealer has “fixed” the problem two times; the first time they put in a new radio b/c they said the radio switch and the ac switch were connected. That “fixed” the problem until it didn’t. The second time, they put in a new thermistor; that was $700. I think the radio cost about $500. Well, that also worked until it didn’t. The way to get the ac to continue to cool is to stop the car, then restart it and the ac comes back on. I am now out over $1200 and the problem is not fixed. The dealer says they cannot test the car when the ac is cooling and that I need to stop in when it is not, but if I am on my way to work, I can’t just drive by the dealer. I have an appointment scheduled for next week to leave the car so that the mechanic can drive it back and forth from work to try to get the ac to fail. But you can’t get it to fail. It just fails erratically.
Any suggestions?

Without knowing what the system pressures are at idle and at elevated RPMs (both high and low sides) and the details behind what was actually done during all of this I cannot say what the problem is.

However, I will say that if you’re serious about 500 PSI and were not mislead on that or have misinterpreted it the system will suffer a lot because of that excessively high figure.
I can’t say as I’ve ever seen or heard of an A/C system reaching 500 PSI no matter what the problem was. Usually things blow up by that point.

OK, sciguy made that comment 2 years ago. This thread has been hi-jacked twice now.

Zoey, besides being a no-no to hi-jacking threads (please start your own to cut down confusion), your problem is electrical. Unfortunately, electrical problems are hard to diagnose, especially when they are intermittent. The best hope to finding the problem is when the system is acting up. Otherwise, they will keep throwing parts at it, and taking money out of your wallet, until the problem goes away. Not a very efficient or cost-effective method.

Thanks for the heads-up on the comment. Sometimes I read the entire threads and sometimes I don’t. Apparently, there’s 2 Subaru posters weighing in with A/C problems on this thread.
My fault for not following the train more closely.