Compressor clutch not engaging

Tiny
WHITEDIAMOND642
  • MEMBER
  • 1995 BUICK LESABRE
  • 100,000 MILES
This is my first time posting here, so I'll be as complete as possible.

The car is a 1995 Buick Lesabre (not sure if it's a Custom or Limited). It has manual climate control, an automatic transmission with a 3.8L V6.

The car's AC system wasn't blowing cold air. I was told the compressor was replaced about two years ago with what appears to be a remanufactured unit.

The first thing I noticed was that the compressor clutch never engaged or even appeared to attempt to when turning on the AC. Below are the diagnosis steps I've performed so far:

1. AC fuse is good
2. When turning the AC on, the relay does "click", but I did not check it beyond that
3. There is voltage (~12v) at the compressor harness (green wire) when the AC is engaged
4. I unplugged the refridgerant pressure switch and jumped it to ensure it wasn't an issue with freon level and found voltage at the compressor harness when jumped and zero volts when not jumped

At this point, my thinking is the compressor clutch being the culprit, but the owner said she never heard any strange sounds coming from the car when the AC was working.

I'm taking another look at it again tomorrow to test the ground connection at the harness thinking possibly it could be the issue as well (my voltage test was grounded at the battery). Beyond that, I'm not sure where else to look.

Is there a part of the electrical diagnosis that I'm missing or am I correct in thinking it's the clutch?

Thanks very much for the help.
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Tuesday, May 7th, 2013 AT 4:37 PM

2 Replies

Tiny
ASEMASTER6371
  • EXPERT
Compressor is your issue. Does not matter if it was replaced. Make sure the ground is good as well.

Roy
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Tuesday, May 7th, 2013 AT 5:14 PM
Tiny
WHITEDIAMOND642
  • MEMBER
Thanks for the reply. That was my original diagnosis, but the owner (a friend of mine) took it to a shop for another diagnosis. They told her (and I spoke with them as well) that they couldn't get voltage to the compressor and thought it was an electrical issue.

This prompted me to take a second look. Again, I found voltage ( 12v) from the green wire while grounded off the black wire on the harness. My thoughts still lie with the compressor.

Just to be 100%, I cut off the harness (which by the the two other splices appears to have been done before) and wired it straight to the battery. Low and behold, the compressor clutch engaged! I started the car and jumped it to the battery again and viola, working AC. This was all done without jumping any of the other switches.

This obviously rules out the compressor/clutch and the only thing I can figure is that there is some sort of voltage drop under load from the harness when the compressor attempts to kick on. Aside from the wiring being spliced with 14 ga wire instead of the stock 18 ga, there doesn't appear to be any issues with the wiring. I can't think of anything else that would cause this.

Ordinarily, I would dig into the wiring to figure this out, but that takes time and I only do this on the side and the owner doesn't have alternate transportation. My thought is to wire in a fused relay from the battery utilizing the stock wiring as the switch. This should do the trick and I can't think of any negative side-affects, aside from the next mechanic cursing me.

Any thoughts to this solution?

Thanks again for the assistance.
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Wednesday, May 8th, 2013 AT 10:59 AM

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