A/C clutch not engaging

2002 CHEVROLET SILVERADO
345,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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PORTER LIBERTY
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Truck listed above is a 2001. So a while back my A/C stopped working. The clutch wont engage. I spent $400.00 on a new compressor, pressure sensors and a charge. Still no luck. I tested the voltage at the low pressure sensor and it was 12v, then at the high pressure .08v from the PCM. Not sure what the voltage is supposed to be at the high pressure switch but i'm sure that .08 is far too low. I've checked all of the wiring, fuses and relay and they are all good. I tested the A/C button and it works and the light comes on. The clutch does engage when I jump pin 30 and 87 on the relay but wont work otherwise. I think it's a PCM problem because A/C request volts are so low, but i'm not positive. I've been working at this for weeks and don't know what else to try. If anyone knows something please let me know, thanks!
Aug 13, 2020 at 7:46 AM
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ASEMASTER6371
  • Experienced Mechanic
  • 52,796 POSTS
Good evening,

If the clutch does not engage when you jumped 30 and 87, you either have no power to 30 or a wiring issue between the relay and the compressor.

I attached a diagram for you.

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

The power for the high pressure switch comes from the control head as in the diagram I just posted. You need to test the power at the control head for power with the key on.

You should also should have power to 2 terminals in the clutch relay as well.

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

https://www.2carpros.com/articles/how-to-check-wiring

Can you verify this?

Roy
Apr 30, 2021 at 9:03 AM
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