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New R4 compressor in 1981 Chevy truck.

hondaman on Fri April 08, 2011 6:12 PM User is offline

Year: 1981
Make: Chevy
Model: C10
Engine Size: 305
Refrigerant Type: r134a
Ambient Temp: 90
Pressure Low: 45
Pressure High: 220
Country of Origin: United States


I just installed a new R4 compressor. I have it all charged up, but it doesn't seem to be cycling. It stays on, and it's getting really really hot. I'm used to AC compressors cycling on and off. Is everything ok?

GM Tech on Fri April 08, 2011 7:57 PM User is offline

At 90 deg ambient and high blower, suction at 45psi, you won't cycle.....

If you want to see if it cycles, take some heat load away from it-- turn blower on low inside air and water down condenser-(or point it toward wind, or use a box fan) then suction pressure should drop low enough to allow it to cycle---

I am assuming this is a cycling system....and not a POA or other--1981 was a little before my a/c time..

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......

Edited: Fri April 08, 2011 at 7:58 PM by GM Tech

CorvairGeek on Fri April 08, 2011 10:17 PM User is offline

Oh yeah, '81 is a CCOT system, though I don't recall if it cycles on pressure or if it cycles on temperature like my '78 truck does. My '78 Impala cycled on temperature too (though it had a A6) but it didn't even have a low pressure cut off switch, mechanical thermostat only.


2005Equinox on Sat April 09, 2011 1:30 AM User is offline

This one I believe cycles by pressure. My 1981 Bonneville does. I think most R4s run this way. The A6's ran by temperature.

2008 Chevrolet Impala LS
1981 Pontiac Bonneville

2007 Sears Craftsman Lawn Tractor

1985 Chevrolet Caprice

1986 John Deere 165 lawn tractor

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