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Chris (aka-Moose)
Chris (aka-Moose), Technician
Category: Car
Satisfied Customers: 1081
Experience:  16 years of experience
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I have a GMC Denali that has been having AC issues, Yes, it

Customer Question

I have a GMC Denali that has been having AC issues
JA: Have you checked the Freon level?
Customer: Yes, it blows ice cold air and works great, but sometimes it doesn't work at all. I had a loose wire at one time, but that was fixed.
JA: What is the model/year of your GMC?
Customer: 2002
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: We traced wires, found noting wrong. Jumped out the clutch and it seemed to not be working. Changed the Ac clutch yesterday and still have the same problem. The clutch will spin on starting the truck, w Ac on, and then stop.
JA: Anything else you think the mechanic should know?
Customer: Also switched out the relays in the fuse box to see if that made a difference. It didn't
Submitted: 7 months ago.
Category: Car
Expert:  david craig replied 7 months ago.

Hi Im David, thanks for visiting the site. It sounds to me like the evaporator temperature sensor is malfunctioning. a symptom of a problem with the evaporator temperature sensor is fluctuating temperatures from the AC system. If the evaporator temperature sensor sends an incorrect or erratic signal to the computer, it can cause the AC temperature to behave erratically. The temperature may suddenly alternate between cold and warm, which will result in additional strain on the compressor, as well as consistently less cool cabin temperatures.

Customer: replied 7 months ago.
I Don't have fluctuating temperatures. When the Ac comes on, it's ice cold and does fine. Then it will work for days/weeks or it may just not come on the next time we get in the truck. When it doesn't come on, I can see that the compressor is not engaged.
Expert:  david craig replied 7 months ago.

Ok, then you need to check the air gap on the clutch assembly on the front of the compressor. it needs to be .020-.030 if its close to either end it, the gap might be changing with engine temperature fluctuations. you would need to replace the compressor if thats the case or you can pull the compressor and have a shop re shim it by either adding or subtracting a shim.

Customer: replied 7 months ago.
The air gap is .025-.028 I checked it with a gauge as we installed the clutch. It came with 3 shims, two were thin, one was thicker. I tried the thin and thick but the gap was too much. So I changed it to 2 thin ones and it was perfect
Expert:  david craig replied 7 months ago.

and is the ac fully charged? and is it working right now?

Customer: replied 7 months ago.
The Ac is fully charged. It is not working. The clutch will spin on starting the truck, whether the Ac is turned on or not, and then stop. We get no voltage at the compressor plug. The relay is good. The pressure switch also checks as good
Customer: replied 7 months ago.
If the wire to the compressor is bad, how can I override or jump it out?
Expert:  david craig replied 7 months ago.

you can make sure its the witing and not the clutch relay by putting a jumper in the relay base 30 to 87. if the compressor turns on then you will need ot swap the relay out with another. if it doesnt turn on you need a another compressor

Customer: replied 7 months ago.
Jump it while it is running?
Expert:  david craig replied 7 months ago.

yes

Expert:  david craig replied 7 months ago.

or with the key on

Customer: replied 7 months ago.
Ok, I jumped the relay, and the compressor kicks on. I traded out the relay with one of the four in the box and the compressor did not turn on. I then traded it with another and it still did not kick on. It only kicks on with a direct jump
Expert:  david craig replied 7 months ago.

ok so we know the wiring from the relay is good and the compressor is good. let me get a plan together

Expert:  david craig replied 7 months ago.

heres a print to help you understand how it works

Expert:  david craig replied 7 months ago.

check that IGN E fuse

Expert:  david craig replied 7 months ago.

just checking in, hows it going?

Customer: replied 7 months ago.
I had to work today, haven't had a chance to do anything today yet. Thank you for checking though. I'll tell you what I find out tonight.
Expert:  david craig replied 7 months ago.

ok, thanks

Customer: replied 7 months ago.
Checked the fuse this morning and it is fine
Expert:  david craig replied 7 months ago.

ok I know you said the system is blowing ice cold when working, but you need to put a manifold gauge set on it so we can check the high and low side pressures statically. this is a must before we go any further.

Expert:  david craig replied 7 months ago.

hows it going?

Customer: replied 7 months ago.
Trying to run down my set of gauges. Haven't seen them since we moved in December.
Expert:  david craig replied 7 months ago.

ok....just checking in

Customer: replied 7 months ago.
Pressure is 250 and 60
Expert:  david craig replied 7 months ago.

60 low 250 high?

Customer: replied 7 months ago.
Customer: replied 7 months ago.
That was with the compressor jumped out and running
Expert:  david craig replied 7 months ago.

it didnt cycle?

Expert:  david craig replied 7 months ago.

whats the outside temp?

Customer: replied 7 months ago.
80 I think. It didn't cycle, just ran as long as it was jumped, then quit as soon as we pulled the jumper
Expert:  david craig replied 7 months ago.

low side way too high

Customer: replied 7 months ago.
it is. My guy said prob over charged about a pound
Expert:  david craig replied 7 months ago.

was the inside air cold while it was jumpered?

Customer: replied 7 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 7 months ago.
Call(###) ###-####if that is easier than texting
Expert:  david craig replied 7 months ago.

let some refrigerant out til the pressure drops to 40

Expert:  david craig replied 7 months ago.

i dont think im allowed to call without offering the premium service. which is 26.00 extra

Expert:  david craig replied 7 months ago.

i dont set the fees...the site does.

Customer: replied 7 months ago.
Nah then this is fine. I'm not by the guages anymore, but I can let some out
Customer: replied 7 months ago.
Air was blowing cold while we did the checking
Expert:  david craig replied 7 months ago.

try that. let me know if it works ok after that. might be looking at a pressure switch problem if you get the pressure down to 40 and it still isnt working.

Customer: replied 7 months ago.
That's what the my mechanic friend was saying too
Expert:  david craig replied 7 months ago.

brilliant minds think a like...lol