GM Truck Club Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
Okay, cruising down the road and all of a sudden my air conditioner starts blowing hot air. Florida is no place to be without air conditioning. Then I look down and all the guages are out of commission. Every guage is off and not working at all. Everything is operating, motor is running fine, but no air conditioner and no guages. I am on a day trip to Georgia and nowhere near home. I find a shop and the guy hooks up the code reader and starts checking things. Started the motor up and all the guages started working but no AC. The guy checks the fuse board and finds that if he grounds the fuse, the AC starts working but when he moves the screwdriver it quits again. His diagnosis is "it's either the computer or the fuseboard". Since the engine and everything else is working I come on home. What does everyone think could be the problem?
 

·
Registered
Joined
·
2,823 Posts
Billy Ray, Need more info like year, model, engine size etc. Also what fuse was he grounding? Did he tell you of any codes from his scanner?
 

·
Registered
Joined
·
4 Posts
Discussion Starter #3
2008 Envoy, 6 cylinder engine. The fuse he was grounding was one of the little gray box type and I assume it was the air conditioner fuse. He did offer to run a toggle switch into the car as a manual switch but I graciously declined the offer.
 

·
Registered
Joined
·
2,823 Posts
Billy Ray, that little gray box is not a fuse, it is the AC compressor relay and its in the middle of the fuse box I think. I don't have a wiring diagram for your vehicle but will look around the net for one. I believe the ECM controls that relay.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #5
You are right. It is in the middle of the box. So how big a job is it to replace it or whatever they have to do.
 

·
Registered
Joined
·
2,823 Posts
Bill Ray, the AC compressor clutch is operated when that AC relay operates. The AC relay operates from a signal out of the ECM. The ECM in turn responds to a PSI signal from the AC refrigeration line sensors. I believe there are 2 of them. One for high pressure and one for low pressure. You need an air conditioning guy to fix this for you. It may be that the refrigerant pressure is low, so the low pressure sensor tells the ECM to shut off the AC. It could even be that the pressure sensor(s) are bad and hence the same problem. The AC relay could be defective too. The ECM on these vehicles is pretty stout so I wouldn't touch that unless it is a last resort or proven defective by a competent technician. They are expensive.
Do not wire in a switch to that relay as that will definitely cause more issues if the AC charge is low etc.
 

·
Registered
Joined
·
2,818 Posts
The magic words are in post # 1 " The guy checks the fuse board and finds that if he grounds the fuse, the AC starts working but when he moves the screwdriver it quits again." It is not the fuses or ECM, forget those issues, start cleaning you engine bay grounds for a start.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #8
Update on the Envoy Air conditioner. Got up and took it to the shop to leave it with the guy. On the way, I tried the A/C just for kicks. It started fine and everything has worked fine every since. The guy said " I can't fix what I can't find so when it acts up again, bring it back".
 

·
Registered
Joined
·
2,823 Posts
Billy Ray, that problems seems to have resolved itself but don't be fooled it will return at some point. I hope not but experience taught me otherwise. I would check that fuse box very carefully inside and out. Good luck.
 
1 - 9 of 9 Posts
Top