No power getting to the compressor?

LANIC

MEMBER
1991 GMC C3500
V8
2WD
AUTOMATIC
292,000 MILES

The ac on my 91 gmc 1 ton dually has been retro fitted and charged with R134a. It has worked well for the past year. Last week it quit. The truck has a digital display and the ac light started flashing, indicating that the system need to be serviced. I've had the system checked and it is still fully charged. I'm told that there is no power getting to the compressor and this could be a possible relay or fuse problem. How can I check this out, and where are the relays located. (The 25 amp fuse in the fuse block is good)

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

The relay for the compressor is located behind right hand side of the instrument panel. On top of the heater/AC case behind the dash.
First visually check the relay for any corrosion or burnt pin(s).

You can also test the relay as well:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.

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