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I have a GMC Denali that has been having AC issues, Yes, it

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I have a GMC Denali...
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: 1 year ago.Category: Car
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Answered in 21 minutes by:
8/28/2016
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago
David Craig
David Craig, Auto Mechanic
Category: Car
Satisfied Customers: 4,024
Experience: Owner/Mechanic at 3D Automotive
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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.

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Customer reply replied 1 year 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.
Auto Mechanic: David Craig, Auto Mechanic replied 1 year 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.

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Customer reply replied 1 year 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
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

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

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Customer reply replied 1 year 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 reply replied 1 year ago
If the wire to the compressor is bad, how can I override or jump it out?
Auto Mechanic: David Craig, Auto Mechanic replied 1 year 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

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Customer reply replied 1 year ago
Jump it while it is running?
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

yes

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Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

or with the key on

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Customer reply replied 1 year 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
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

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

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Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

check that IGN E fuse

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Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

just checking in, hows it going?

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Customer reply replied 1 year 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.
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

ok, thanks

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Customer reply replied 1 year ago
Checked the fuse this morning and it is fine
Auto Mechanic: David Craig, Auto Mechanic replied 1 year 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.

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Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

hows it going?

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Customer reply replied 1 year ago
Trying to run down my set of gauges. Haven't seen them since we moved in December.
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

ok....just checking in

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Customer reply replied 1 year ago
Pressure is 250 and 60
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

60 low 250 high?

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Customer reply replied 1 year ago
That was with the compressor jumped out and running
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

it didnt cycle?

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Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

whats the outside temp?

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Customer reply replied 1 year 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
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

low side way too high

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Customer reply replied 1 year ago
it is. My guy said prob over charged about a pound
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

was the inside air cold while it was jumpered?

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Customer reply replied 1 year 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 reply replied 1 year ago
Call(###) ###-####if that is easier than texting
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

let some refrigerant out til the pressure drops to 40

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Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

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

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Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

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

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Customer reply replied 1 year ago
Nah then this is fine. I'm not by the guages anymore, but I can let some out
Customer reply replied 1 year ago
Air was blowing cold while we did the checking
Auto Mechanic: David Craig, Auto Mechanic replied 1 year 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.

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Customer reply replied 1 year ago
That's what the my mechanic friend was saying too
Auto Mechanic: David Craig, Auto Mechanic replied 1 year ago

brilliant minds think a like...lol

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