My car A/C is not clutching

Tiny
ROYCAR71
  • MEMBER
  • 1998 GMC JIMMY
  • 4.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
I replaced all my a/c components last year and all worked good. A year later, I get air warm and compressor is not clutching. When I test my pressure with my gauges I get 70 psi on low side and about 35 psi on high side. I jumped wire from compressor directly to battery then it engages and spin and cold kicks on. I swap a/c relay with another working one and it still does not clutch. Checked fuses. Still can not figure out what wrong.
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Friday, April 17th, 2015 AT 2:27 PM

7 Replies

Tiny
ED-WEEZY21
  • EXPERT
Just to clarify, those pressure readings that you're giving us would indicate that you have a pressure problem. The high should be considerably higher than 35. Should be closer to 200. I don't know the exact specs. And the low side should be around 30-35. Best way to check if you don't have a proper gauge is the smaller AC line is the high side and should feel really hot and the low side is the bigger tubing and should feel cold. Have you performed a leak test on the AC system to make sure you are not losing your pressure anywhere because that's what it's sounding like.
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Friday, April 17th, 2015 AT 3:13 PM
Tiny
ROYCAR71
  • MEMBER
I checked pressure and I have enclosed a picture with actual reading. Low port is 85 psi and the Hi port is 90 psi and I don't think I have a leak because the pressure on the gauge held more than 30 minutes. I do not feel cold or warm temperature on either one of the lines either.
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Friday, April 17th, 2015 AT 11:03 PM
Tiny
ED-WEEZY21
  • EXPERT
Are you reading the pressures with the vehicle running or the engine off?
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Saturday, April 18th, 2015 AT 7:24 AM
Tiny
ROYCAR71
  • MEMBER
Off
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Saturday, April 18th, 2015 AT 5:44 PM
Tiny
ED-WEEZY21
  • EXPERT
I would take it to a pro in electrical and check if you have any opens or shorts in the HVAC circuit since you said bench testing the compressor proved that the compressor worked.
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Sunday, April 19th, 2015 AT 1:35 PM
Tiny
ROYCAR71
  • MEMBER
I agree on that. One last question. Even though I jumped directly from battery compressor just spinned and enagaged but it did not clutch on and off. Is that noramal for compressor to work like that.
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Sunday, April 19th, 2015 AT 9:18 PM
Tiny
ED-WEEZY21
  • EXPERT
I'm not sure if the compressor should clutch on and off when bench testing. I would believe it wouldn't because it needs to also receive inputs from the ecm to clutch based on other factors of the vehicle like temperature or load.
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Monday, April 20th, 2015 AT 3:55 AM

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