Air conditioner compressor will not kick on

JSTEBBINS

MEMBER
1999 CHEVROLET LUMINA
3.1L
V6
2WD
AUTOMATIC
85,000 MILES

System charged, pressure switch good (new), relay good (new) air conditioner compressor will not kick on on its own. I can bypass the relay and it blows cold air but will not run otherwise. Everything is sill like new on this car. No corrosion on the fuse relay blocks/ connections, all fuses good. Anyone have anything similar?

5 Replies

WRENCHTECH

MECHANIC
20,757 POSTS

Test your two fuses first. If the fuses check out okay, your next step will require a professional scan tool to look at data and determine if the PCM is getting the "ON" request from the Control Head.

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Friday, August 5th, 2016 AT 6:00 AM

JSTEBBINS

MEMBER
3 POSTS

If it ends up being the PCM, can a used one be purchased and installed without reprogramming? Plug and go?

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Monday, August 8th, 2016 AT 7:16 PM

WRENCHTECH

MECHANIC
20,757 POSTS

No, it can't but why would you even suspect the PCM. That is the least likely cause of your problem.

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Monday, August 8th, 2016 AT 7:19 PM

JSTEBBINS

MEMBER
3 POSTS

Because everything else has been replaced and is working. The cooling fans also kick on shortly after start up and run all the time whether the air conditioning is on or not. I am not saying that is the problem but after all that has been done it's pointing in that direction. I am thinking my next step should be getting it to someone who can stand the PCM and see what it is doing

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Tuesday, August 9th, 2016 AT 9:08 AM

WRENCHTECH

MECHANIC
20,757 POSTS

As I said, that is not not likely at all. I live in South Florida and I have been repairing AC for over 40 years and I have yet to Replace a PCM for inop AC. You need someone with electrical knowledge to track it down by following the wiring diagram and a scanner.