Compressor clutch will not engage

Tiny
DILCH
  • MEMBER
  • 2006 GMC SIERRA
  • 6.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 153,000 MILES
Truck listed above is a 2500. Changed compressor, dryer, condenser, pulled vacuum, filled with Freon. Compressor won’t com on unless jumped at relay. Changed fuse block. Checked fuses. Need the article on how to check voltage on pressure switch and command to relay. Have 3 pin high pressure switch and 2 pin cycling switch. Took it to Knick car they said it had Freon. They used recover device, emptied, pulled down add Freon and couldn’t figure out. Can I check at pin 85 to see if PCM is signaling to ground. Fred
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Sunday, July 25th, 2021 AT 5:50 AM

2 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good evening,

I attached the wiring diagram for you of the system.

Go to the relay and remove it. There should be 2 pins with voltage with the key on. You need to verify that.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

https://www.2carpros.com/articles/how-to-use-a-voltmeter

The pressure switch should have 2 5 volt feeds and a ground.

Roy
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Sunday, July 25th, 2021 AT 5:37 PM
Tiny
KASEKENNY1
  • EXPERT
Okay. Here are a number of guides that will help with this:

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

The way to test the relay is getting grounded is to remove the relay and put your red meter lead on battery positive (or terminal 86) and the black lead on pin 85 and then start the engine and turn the A/C on. You meter should read 12 volts. This shows that the PCM is grounding the relay and is functioning properly.

Please run through this and let me know what you find. Thanks
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Sunday, July 25th, 2021 AT 6:25 PM

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