Automotive Air Conditioning Information Forum (Archives)

e9sling on Tue June 26, 2012 2:44 PM

Year: 1998
Make: Chevrolet
Model: Silverado
Engine Size: 5.7
Refrigerant Type: 134A
Ambient Temp: 93
Pressure Low: 40
Pressure High: 90
Country of Origin: United States

need some help please. i have a 1998 silverado with 5.7, the truck has been sitting for about 6 months. went to use the truck and the a/c wasnt working. the hvac control was going out before i parked it so i assumed that was it and replaced it. i unplugged the cycling switch and jumped across it, nothing. changed the a/c relay, nothing. removed the relay and jumped across it and the compressor started working. i assumed it was low on freon so i bought a can and filled it. worked great and blowing very cold air. compressor never cycled off. ran for about 15 minutes the cut off and didnt turn back on. cooled down for about 30 minutes, started truck and a/c was working again with cold air. 15 minutes later cycled off again. borrowed a set of gauges and got 40 on the low side and 90 on the high side while idling. with engine off, low side goes to about 90 and high side doesnt change. im wondering if the guage is messed up. anybody know why it would work for 15 minutes then cycle off and not come back on unless i turn engine off for around 30 minutes?

GM Tech on Tue June 26, 2012 4:23 PM

Wide air gap on compressor clutch....?

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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......

e9sling on Tue June 26, 2012 4:32 PM

i thought that so i "hotwired" the clutch. if it has current going to it, it will engage. i found out the high side gauge i was using is bad. i got a new gauge and now im waiting for the truck to cool off so i can run it again and see what it reads while it is running and when it cycles off

e9sling on Wed June 27, 2012 8:24 AM

got a new set of gauges, 38 low side 180 high side .040 gap on clutch

e9sling on Wed June 27, 2012 8:37 AM

i thought that so i "hotwired" the clutch. if it has current going to it, it will engage. i found out the high side gauge i was using is bad. i got a new gauge and now im waiting for the truck to cool off so i can run it again and see what it reads while it is running and when it cycles off

mk378 on Wed June 27, 2012 8:39 AM

Gap is too wide.

With everything plugged in normal, wait until it is hot and not working, then measure if power is being applied to the clutch.