Automotive Air Conditioning Information Forum

I was diagnosing this truck yesterday. Compressor clutch wouldn’t engage. Two ac fuses in the cab checked good. Two smaller fuses under he hood checked good. The great big 30 amp fuse was gone. Installed a 60 amp for testing purposes and still no power at the clutch. Tried the ac relay where the horn relay goes and the horn worked so I think the ac relay is good. I used a jumper wire where the relay goes and I can energize the clutch. I did this with the engine running and it killed the motor. Safe to say compressor is locked up tight. When I check for voltage and ground where the relay plugs in, one is hot all the time, one goes to the clutch, and nothing at the other two. No ground or incoming voltage to activate the relay. Forgot to add before doing all this, I vacuumed the system and added some dye and a little refrigerant. Had the switch at the accumulator jumpered.
Any ideas where I should look next?

if you think the compressor is locked up unplug it and put a lamp in its place. Do not use a 60 amp fuse in place of a 30 amp. Too much of a difference and you can let the magic smoke out.

Installed new compressor, condenser, accumulator, orifice tube, hvac control module, and a 30 amp fuse. Only get power at the clutch if I jump the two pins at the relay. It doesn’t kill the motor anymore when I jump the pins at the relay.

There is a pressure switch on the back of the compressor.

I have put 24 oz of refrigerant in the system. Had to use a jumper wire at the relay to get the compressor to run though.

Found the problem. Found another fuse that had been removed. IGN E is how it was labeled. Installed a 10 amp fuse and everything worked.

Thanks for the replies.

Dgreen wrote:Found the problem. Found another fuse that had been removed. IGN E is how it was labeled. Installed a 10 amp fuse and everything worked.

Another GM "secret". Like the fuse for the ECM/OBD2 on my '94 Suburban was also the one with the label "Cigar" for the lighter.