AC problems

[kami333]

The AC on my recently purchased 1993 Impreza wasn't working and I figured out that at least part of the problem was that the refrigerent was low (there was still some pressure in the system). So I topped it off today and the got the compressor turning but it still won't cool down. Didn't have a gauge for the high side so I don't know what sort of pressure I have on that side.

 

Could the compressor have seized even though it doesn't make any noise and the pulley turns?

 

Or is it possible that I have some sort of clog somewhere in the system, like in the dryer or the expansion valve?

[nipper]

It can be contaminated with moisture. You cant just fill up a system without using proper gauges. The gauges tell you lost of information besides pressure.

 

 

nipper

[OB99W]

[...]The gauges tell you lost of information besides pressure.

Kami333, it helps to keep a topic in one thread. Nipper, even without gauges, there's already lots of information ; see: http://www.ultimatesubaru.org/forum/showthread.php?t=78753

[porcupine73]

Is your system R12? Some people just put R134A into such a system, though it really should have the Subaru conversion kit used.

[kami333]

It can be contaminated with moisture. You cant just fill up a system without using proper gauges. The gauges tell you lost of information besides pressure.

 

 

nipper

 

Thanks nipper. I was originally using just the gauge that came with the refill kit (low side only) so I rented a gauge and hooked it up. It shows as good pressure on the low side but the high side is low with the compressor running so am I correct to assume that something in the compressor (reed valve, cylinder, etc) is toast? I assume that it's better to just get a new compressor rather than to try to fix the old one?

 

Good thing is that it doesn't have seem to have lost any refridgerant from yesterday so hopefully there aren't any leaks to track down. There isn't any way to figure that out without putting everything together and pulling a vaccum, right?

 

Kami333, it helps to keep a topic in one thread. Nipper, even without gauges, there's already lots of information ; see: http://www.ultimatesubaru.org/forum/showthread.php?t=78753

 

Sorry, didn't really see how my previous post about whether the adapter was a R134A one was relevant. I'm not a huge fan of threads going off topic, makes searching for threads harder since you have no idea if the title has anything to do with the contents of a thread.

 

Is your system R12? Some people just put R134A into such a system, though it really should have the Subaru conversion kit used.

 

It has a R134A connector on the low side so I've been going on the assumption that someone had done a conversion, whether they did it correctly or just filled it up I don't know. I was trying to avoid having to take it apart but now it seems like I have to.

[OB99W]

[...]I rented a gauge and hooked it up. It shows as good pressure on the low side but the high side is low with the compressor running so am I correct to assume that something in the compressor (reed valve, cylinder, etc) is toast? I assume that it's better to just get a new compressor rather than to try to fix the old one?[...]

It's hard to tell with what you provided so far; more info would be useful. Actual gauge readings (numbers, not "good pressure" and "low"), ambient temperature, engine RPM, etc., are things that would help with the diagnosis.

 

Does the compressor clutch remain engaged, or does it short-cycle?

 

What are the low-side/high-side static pressures? They should be equal if the system has been off for a reasonable period. Then run the system for several minutes, get the gauge numbers (and ambient temp), then shut the A/C off. Determine how long it takes for the low and high side static pressures to again equalize.

 

 

Sorry, didn't really see how my previous post about whether the adapter was a R134A one was relevant. I'm not a huge fan of threads going off topic, makes searching for threads harder since you have no idea if the title has anything to do with the contents of a thread.

Your previous post gave clues to the probable refrigerant "conversion", possible mix of refrigerants, and likely lack of knowledge and/or questionable practices by whomever did the work. Without that information, someone reading this thread might have assumed that the system was an original R12 one.

 

 

It has a R134A connector on the low side so I've been going on the assumption that someone had done a conversion, whether they did it correctly or just filled it up I don't know. I was trying to avoid having to take it apart but now it seems like I have to.

Exactly my point . However, having the readings I asked for above may help to determine just how much work may be needed.

[kami333]

About 42psi on both sides before starting car. Idling at about 900rpm (a little high but seems fine), ambient temp 67degress F, low side was at at 35psi and high side at about 50psi, adding more refridgerent doesn't change difference, at 40psi on the low side the high side is about 55psi. Clutch engaged the entire time, no squealling or other wierd noises from belts or compressor. System equalizes in about 10min.

[nipper]

You may need a new reciever/drier and to have the system flushed. There is a expansion valve. The expansion valve ( or in cheaper systems an orafice is used) may be stuck open by debree. The reciever/dryer is filled with desicant that tends to fall apart if too much outside air/moisture gets into the system. The expansion valve also controls the pressure differntial between high and low sides. It is also possible that it is bad.

 

http://www.hvacmechanic.com/txv.htm

 

Expansion valve operation is the same in all cooling systems.

 

nipper

[porcupine73]

If you need a new drier/receiver you might just want to get the proper conversion kit from Subaru which includes a new drier/receiver. The whole proper conversion procedure is available on endwrench.com

 

My favorite in the EndWrench article on conversion is "Paint the receiver/drier sight glass with touch-up paint. The sight glass cannot be utilized in testing R-134a performance."

 

Do you think black electrical tape would work?

[nipper]

If you need a new drier/receiver you might just want to get the proper conversion kit from Subaru which includes a new drier/receiver. The whole proper conversion procedure is available on endwrench.com

 

My favorite in the EndWrench article on conversion is "Paint the receiver/drier sight glass with touch-up paint. The sight glass cannot be utilized in testing R-134a performance."

 

Do you think black electrical tape would work?

 

 

*snicker*

 

nipper

[kami333]

One thing I forgot to include was the high side pipe coming out of the compressor does not get noticably warm at all, it stays about the same temp as the low side going in.

 

Is it true that if it is something compressor related I should be seeing a fluctuation in the pressure on the high side? Mine was holding pretty steady but since it was so low I don't know if I would have seen it.

 

So at this point it could be the drier/reciever (easy and cheap), expansion valve (under dash, hopefully can be done without taking apart dash), or compressor (rather expensive)?

 

Anyone know if you can get to the expansion valve on a GC-era Impreza without taking apart the dash (I think it says to do that in the manual), I know with newer Imprezas you can get at it from the glove box?

 

Game plan: take out expansion valve and see if it is stuck open. I read that if you stick the thermo probe into warm/cold water you can cycle the valve to make sure it works, does this seem right? If so replace and replace drier as well, vaccum and refill.

 

And I got quoted about $200 for the conversion kit and it didn't seem like anything special that you can't pick up at any auto parts store, other than the drier.

[nipper]

Correct on the test, but you can do the same thing by holding it in your hand.

 

Compressors rarely go bad on soobies, so just by the odds, we can rule that out. If it DID go bad (they don't go quietly into that still night) you wouls still need the system flushed out, and a new dryer and possibly valve. When they go bad they tend to self destruct and thow metal through the system. The compressor is like the engine. Have a hole in a piston or a stuck valave, a vacume needle would bounce. Thge same is true for the AC compressor.

 

I dont even recall the last time somone had a bad one here.

 

The valve should be accessable by taking the cover off the heater core cover.

 

Dumb Question, is the AC compressor clucth engagaing?

 

nipper

[kami333]

Yup, it engages. It wouldn't at first since I guess the refridgerant level was too low but it engages and stays engaged without cycling, even when I ran it for like 30min yesterday.

[nipper]

Yup, it engages. It wouldn't at first since I guess the refridgerant level was too low but it engages and stays engaged without cycling, even when I ran it for like 30min yesterday.

 

Ok just checking, as my shop said to me today "sometimes we miss the obvious"

 

 

 

nipper

[OB99W]

About 42psi on both sides before starting car.

Take a look at the P/T charts at http://www.chillers.com/PT%20charts%20for%20refrigerants.htm . Note the pressures at 65F and 70F for both R12 and R134a; you should be seeing more than 42 psi static. Although static pressure is not the way to determine the proper level of refrigerant charge, it would seem you're still low. How much did you add? (However, be aware that air and moisture affect static pressure.)

 

 

Idling at about 900rpm (a little high but seems fine), ambient temp 67degress F, low side was at at 35psi and high side at about 50psi, adding more refridgerent doesn't change difference, at 40psi on the low side the high side is about 55psi. Clutch engaged the entire time, no squealling or other wierd noises from belts or compressor. System equalizes in about 10min.

Those numbers, of course, aren't "right"; even with the system running and measuring the high side, you're not hitting the expected static pressure for the temperature. Taking 10 minutes for the pressures to equalize after shutdown is excessive; that could help confirm there's contamination in the system, possibly air, moisture, bits of desiccant, etc. As others have already suggested, the system should probably be flushed, receiver/dryer replaced, other parts checked for blockage, etc. Once you're sure things are clean and dry, evacuate and recharge -- and don't forget the correct refrigerant oil type and amount.

[Blue Whale]

 

Compressors rarely go bad on soobies, so just by the odds, we can rule that out. If it DID go bad (they don't go quietly into that still night) you wouls still need the system flushed out, and a new dryer and possibly valve. When they go bad they tend to self destruct and thow metal through the system. The compressor is like the engine. Have a hole in a piston or a stuck valave, a vacume needle would bounce. Thge same is true for the AC compressor.

 

I dont even recall the last time somone had a bad one here.

 

nipper

 

I had one go bad on a '93 Legacy a few years ago--just over 100,000 miles, on a trip to Oregon, it suddenly froze up (quietly into the still night, actually); from the way it felt, I believe it was mechanical breakage (with the clutch engaged, slight play either way, then no further movement possible). There was never an AC issue before that, and the system didn't leak then or thereafter (I had a shop remove the R-12, changed the compressor, retrofitted the valves, and refilled with R-134a; the system worked fine). Subarus can have various brands of compressors, so experiences may vary. My '95 has a compressor identical to the one that failed--no problem with that one. Anyway, compressors can fail, and they can fail in a self-contained way as mine did, without damaging anything else.

[nipper]

I had one go bad on a '93 Legacy a few years ago--just over 100,000 miles, on a trip to Oregon, it suddenly froze up (quietly into the still night, actually); from the way it felt, I believe it was mechanical breakage (with the clutch engaged, slight play either way, then no further movement possible). There was never an AC issue before that, and the system didn't leak then or thereafter (I had a shop remove the R-12, changed the compressor, retrofitted the valves, and refilled with R-134a; the system worked fine). Subarus can have various brands of compressors, so experiences may vary. My '95 has a compressor identical to the one that failed--no problem with that one. Anyway, compressors can fail, and they can fail in a self-contained way as mine did, without damaging anything else.

 

Maybe i am just used to american ones that scream like a tortured squirrel

 

nipper

[avk]

There may be enough pressure not to trip the cut-out switch, but the charge can be still low. Low charge is the simplest thing to assume, esp. if the liquid line is not getting hot to the touch.

[Blue Whale]

Might the compressor clutch be slipping?

[kami333]

A/C now fixed! Thanks all.

 

It turned out to be the compressor after all, clutch would engage and turn freely but apparently it wasn't compressing (didn't think that was possible but oh well:confused: :confused: ). At least I ended up changing out the evaporator so all the gunk that was in there is cleaned out and all O-rings changed and it held vaccum while I went to go get more refridgerant so it looks good.