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GMC AC on and OFF

inventorb on Mon August 19, 2013 3:00 PM User is offlineView users profile

Year: 2005
Make: GMC
Model: Seirra HD 2500
Engine Size: 6.0
Refrigerant Type: 134a
Pressure Low: 34
Pressure High: 200
Country of Origin: United States

Text My A/C works fine normally in my Truck.
I have checked Hi side and low. Needles are steady and no signs of blockages.

The A/C is definitely cooling the air then for no reason known it stops and blows hot.

However, when it does stop working I park the truck overnight go out in the morning and the AC is working fine. It has occurred twice now. Just drove over 1000 miles on a trip and no issues. I am puzzled! I have check connections, low side readings high side readings and all are within normal range. The clutch seems to be working correctly.

One Nickle is more than No Nickles. And a Billion Nickles is allot of money.

Olds442 on Mon August 19, 2013 10:21 PM User is offline

Check the air gap on the clutch.

Cussboy on Mon August 19, 2013 11:33 PM User is offline

Originally posted by: Olds442
Check the air gap on the clutch.

Yeah, when the AC stops working right, leave it on and open the hood, visually see if the center part of the AC compressor is turning the same speed as the belt/outside rim of the pulley.

I had similar such issue on my Mazda truck a few years ago, and the compressor nut was actually loose, that's all. I was all prepared and practiced to install one of my used AC clutches on while the compressor was still in my truck, even had to make my own puller tool. But I never got to that stage, as when I went to remove the shaft nut, found it had loosened !!!

webbch on Tue August 20, 2013 12:15 AM User is offlineView users profile

I'll admit a stupid mistake....when I plugged the connector into my compressor on my '90 chevy 5.7L, I installed the prong on the compressor between the rubber boot and one side of the female connector, rather than INTO the connector. Worked fine for a day or so, then started blowing warm. Easy fix once I noticed the mistake. An unlikely case unless you've touched it recently. Air gap far more likely scenario.

Edited: Tue August 20, 2013 at 12:15 AM by webbch

GM Tech on Tue August 20, 2013 7:56 AM User is offline

Very common issue- crawl under your truck next time it is off when it should be on- and whaaaaap front of driver with a wooden hammer handle- if it engages then you have the worn, wide air gap- then pull off clutch driver and remove the widest shim- replace and be good for another 100k. I've done a dozen or so just like yours..

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

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