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The A/C clutch engages when the vehicle is turned off?

Tiny
RBSMITH1015
  • MEMBER
  • 1991 CHEVROLET 1500
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 300,000 MILES
The A/C clutch engages when the vehicle is turned off draining the battery.
I can disconnect the A/C cycling switch and it will disengage. I replaced the cycling switch thinking that was the problem, but I was wrong. I put a test light on one side of the and there is power to it even though the vehicle key switch is off.
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Thursday, August 18th, 2022 AT 2:36 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,072 POSTS
It sounds like the HVAC control module has gone out. Here is the wiring diagrams for the system so you can see how it works and I have included how to change the module out in the images below. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
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Thursday, August 18th, 2022 AT 11:20 AM

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