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Another Subaru with an A/C Problem

Funny that there’s another Subaru on here today having an A/C problem, though it doesn’t look like it’s the same problem.

I’ve had my Subaru for 8 yrs and never had a problem with the A/C, even in 100+ degrees of Arizona. I always had to turn down the temp. I’ve been in Maryland for nearly 4 yrs and it’s worked fine even on very hot and humid days. In March I noticed that it didn’t seem as cold as usual. I also didn’t hear the compressor coming on when I turned it on. Mechanic checked it out and said the compressor was working but it probably just needed freon (I hadn’t added any since I bought the car). They added a dye in case there was a leak and said I’d be able to tell in 2 weeks if it was leaking, but that the dye is greasy and might actually fix a leak if it’s just due to a dry seal somewhere. They didn’t charge me for the freon. (These are honest mechanics. I’ve been with them for several years and they’ve had numerous chances to bilk me but never have.)

Couple weeks went by and it seemed okay, though maybe not quite as cold as when I picked it up. Sometimes I’d drive and it would be very cold so I’d think it was fine, but a few minutes or some time later I’d know for sure it wasn’t right. The weather vascilated between hot and cold too, which made it harder to tell. Finally the past 2 weeks it got really hot and I knew for certain it wasn’t putting out cold enough air. Yesterday was in the low 90’s and I was sick from the heat while driving. Only felt like a fan blowing. I left it at the mechanic’s today. They just called and said the vent temp is normal and there are no leaks. They’re going to check for an electrical problem, as I also have a brake light that blows on a regular basis. (Though he said those aren’t on the same circuit)

As far as my operating behavior, I don’t turn it on and off all the time, and once it’s going for a few minutes I put in on recirculate. I’m the only driver.

1999 Subaru Legacy sedan, 160K miles

(Sorry for the multiple posts of this question! Nothing happened when I clicked “Post” so I clicked it again. And again.)

It could be a bad pressure switch. These units are designed to shut off if the pressure is too low or too high to help preserve the compressor. So if one of these switches was misreading the Freon pressure, or if you were on the jagged edge of where you should be high or low, temperature swings can push you over the edge and shut you down. This would explain why the problem is intermittent. What may also work to test this theory is parking the car outside all day and letting it heat up, then trying the AC. Again in the AM when its cool out the pressure may be fine and all is ok, but as it heats up and the pressure goes up (hot gasses expand) its just enough to kick the high pressure switch. So the two things too check is, the right pressures in the system, and B those switches.

Thanks so much. I called the mechanic and they’re about to test it after leaving it in the hot sun for an hour. Hoping they can track down the problem and fix it easily.

Is a pressure switch expensive if that’s what it turns out to be?