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AC not working when activated in the cab
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Repute3619
Novice
Jun 13, 2012, 8:05 PM
Post #1 of 5
(2384 views)
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AC not working when activated in the cab
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My vehicle is a 1997 GMC Sierra SLE V8 5.7L w/ ~103,000 miles.
With the weather here in Indiana starting to get quite uncomfortable for longer trips, I am looking to fix a problem I have had for about a year now.
My AC stopped outputting cold air into the vehicle last spring, I had it checked for leaks (passed) and then recharged during the same visit to the service shop. It worked great for a couple of weeks with usage every other day for about an hour a day to and from work and basic traveling. The compressor stopped running under the hood at that point. I then tried hooking it directly up to power and it worked fine. I then checked the pressure of the coolant and it had seemed to drop significantly. I am unsure where to go from this point.
I was hoping someone might be able to tell me what it might be that would cause this. I thought perhaps a sensor or the in dash panel, but was hoping for some input prior to beginning replacing part after part with no real direction. I was hoping to avoid replacing the compressor itself if at all possible due to high cost. Any input would be appreciated, and as always, thanks in advance for any help.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 14, 2012, 2:10 AM
Post #2 of 5
(2335 views)
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Re: AC not working when activated in the cab
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The most common reason for inop compressor is due to low pressure from a leak. See if power gets to LPCO = low pressure cut out on the accumulator first. If so then we would need a plain static pressure meaning cold engine, off, just take the pressure like checking a tire. It really should be close in PSI as the temp underhood in Farenheit. Actually shouldn'd be cooling at all or much if low.
Static pressure just means there's some in the system not that it's full. Operating pressures are more telling. It worked so suggest if you don't want this go get expensive any more than it would or could be to find the likely leak.
#1 spot is on a Delphi compressor if still the original or replaced already with one again is body gasket leaks but could be anywhere refrigerant is.
How did you check or think the system is low? You need to post more exact actual pressures when operating. If that static pressure is too low compressor will not engage.
If when forced and compressor noisy unplug it as it will self destruct running low on refrigerant which carries the oil to save compressor from burning out throwing junk thru system. This condenser can't effectively be flushed out like many out there.
You can look for oily spots on anything that carries refrigerant. That's a clue. It may have passed as you said and be a new leak by chance or just missed in checking.
If you find the this problem to be a leak know that it really wants exact refill by weight. Unknown right now but if a compressor IMO the better replacement is a NEW Sanden and don't mess with remanufactured ones as there are too many failures IMO and experience that set you back to perhaps to worse than before. Be warned this isn't the best DIY thing without pretty extensive understanding and ability with equipment to get it right,
T
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 14, 2012, 5:33 AM
Post #5 of 5
(2293 views)
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Re: AC not working when activated in the cab
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OK, let me ask you this. If your truck was low on refrigerant and your "mechanic" determined there was no leaks, where did your refrigerant go? Did someone steal it?. _____________________________________________________________________________________________________________________________________ HT - The gas is getting pricey so of course people steal it. Even stealing air from tires  Of course joking OP (original poster) careful what you jump to make things anywhere work. I'd sooner see this leak checked again, dye added if not already in there, if difficult to find electronic sniffers can help, even soapy water. Condenser can pick up a bit of road debris anytime. If leaks were ruled out just by it holding a vacuum some will hold a vacuum but not the operating pressures when charged. A two week leak should be fairly easy for a tech to find, T
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