A/C Compressor won't disengage in time

**sewer rat** · 04-15-2009, 07:56 AM

Ever since my 1998 LS1 was rebuilt (after breaking valve spring) the a/c compressor does not disengage at WOT (or does not disengage fast enough). I'm now on my third compressor because it gets over-driven and destroyed at high rpm. Only significant differences in engine after rebuild is GM ls1 hot cam, machined deck, and aftermarket valve springs.

Is compressor disengage controlled by pcm or maybe some separate relay? Can this be fixed by programming? If so, I'm going in for tuning after current installation of new headers, intake manifold and throttle body so I could get it done then. Thanks!!

**9t8z28** · 04-15-2009, 04:24 PM

I know how to fix the problem.

STOP GOING WOT WITH THE A/C ON! Didn't anyone ever tell you that this is bad for it? The compressor certainly cannot disengage fast enough. You keep tearing them up.

**sewer rat** · 04-16-2009, 05:13 AM

Um yeah, thanks for that... Actually, Chevy thought about that and made provisions for the a/c clutch to disengage at wot so rocket scientists like you and me wouldn't have to worry about it. I'm just wondering why mine no longer functions like it used to and how to fix it.

I already have a home-made disconnect switch installed that is actuated by the throttle lever to shut off the a/c at wot, but am trying to find a more "correct" way to do this...

**9t8z28** · 04-16-2009, 08:31 AM

Originally Posted by sewer rat

Um yeah, thanks for that... Actually, Chevy thought about that and made provisions for the a/c clutch to disengage at wot so rocket scientists like you and me wouldn't have to worry about it. I'm just wondering why mine no longer functions like it used to and how to fix it.

I already have a home-made disconnect switch installed that is actuated by the throttle lever to shut off the a/c at wot, but am trying to find a more "correct" way to do this...

It's not rocket science, it's common sense!

And for your info, it's controlled by throttle position.

**sewer rat** · 04-16-2009, 12:06 PM

Ok, thanks. Do you know if the a/c clutch is disengaged by a signal from the PCM (based on throttle position) or is there a separate relay somewhere?

**sewer rat** · 04-16-2009, 12:48 PM

Found answer. There is an a/c compressor clutch relay located in the underhood fuse block that is controlled by the PCM. One of the inputs to the PCM that controls the relay is TPS signal (others are a/c request signal and refrigerant pressure sensor signal). I'll check relay.