Question about AC...
Thread Starter
Intermediate
Joined: May 2004
Posts: 35
Likes: 0
From: Antioch CA
Question about AC...
Hello All,
My 93's AC unit (and plumbing) frosts over after a few hours of running, to the point of (I'm assuming) freezing the vents so I no longer get any air blowing into the car until I turn of the engine and give it a chance to "defrost".
Am I looking at a major repair job or does this sound like something minor (leak, low coolant, too much coolant, etc...)?
Sorry for my less than techincal jargon, I'm not much of a mechanic. :bb
Thanks in advance...
My 93's AC unit (and plumbing) frosts over after a few hours of running, to the point of (I'm assuming) freezing the vents so I no longer get any air blowing into the car until I turn of the engine and give it a chance to "defrost".
Am I looking at a major repair job or does this sound like something minor (leak, low coolant, too much coolant, etc...)?
Sorry for my less than techincal jargon, I'm not much of a mechanic. :bb
Thanks in advance...
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Question about AC... (wwjoyner)
Where exactly is the frost - high side (smaller lines) or the low side (fatter)?
If it's on the high side just before the Evaporator, that's generally a plugged orifice. If it's on the low, the line may be bent or kinked or the low pressure switch is out of whack or improperly adjusted. If it's not cycling off, you might try a new pressure switch. It should be on the evaporator outlet pipe (the bigger one at the top) or on the Accumulator. You don't have to discharge the system to change it as it is on a schrader valve. Just make sure you tell whomever you buy it from that it's for R12 (assuming that what you have in it).
If it's on the high side just before the Evaporator, that's generally a plugged orifice. If it's on the low, the line may be bent or kinked or the low pressure switch is out of whack or improperly adjusted. If it's not cycling off, you might try a new pressure switch. It should be on the evaporator outlet pipe (the bigger one at the top) or on the Accumulator. You don't have to discharge the system to change it as it is on a schrader valve. Just make sure you tell whomever you buy it from that it's for R12 (assuming that what you have in it).
Thread Starter
Intermediate
Joined: May 2004
Posts: 35
Likes: 0
From: Antioch CA
Re: Question about AC... (SunCr)
Hi SunCr,
The frost is visible on the small lines on top. It's also on the "module" right next to the firewall.
I'll be ordering a shop manual this week but if I'm not able to figure out how to replace the pressure switch (or that turns out not to be the problem), I just got the names of a couple of local Corvette-only shops that I'll take it to.
Thanks for the fast response (this forum has been very helpful). :)
The frost is visible on the small lines on top. It's also on the "module" right next to the firewall.
I'll be ordering a shop manual this week but if I'm not able to figure out how to replace the pressure switch (or that turns out not to be the problem), I just got the names of a couple of local Corvette-only shops that I'll take it to.
Thanks for the fast response (this forum has been very helpful). :)
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Question about AC... (wwjoyner)
I'm going to guess that the small lines on top are the suction or low side of the system. The module at the firewall is the evaporator. I'd suspect the low pressure switch may be faulty and I'd try a new one first . If it isn't shutting off the system when the pressure drops to 25 psi, it's going to ice up. It's simple to replace. Just remove it as rapidly as possible so the charge doesn't leak out. Don't overtighten the new one either (handtight and 1/4 only) and it helps if you put a little compressor oil on the o-ring (mineral oil if the charge is R12). I know that can be a little expensive since compressor oil is usually only available by the quart and once it's exposed to moisture it will deteriorate pretty fast.
