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A/C will not turn on unless relay is jumped?

Tiny
SHON8088
  • MEMBER
  • 2002 CHEVROLET AVALANCHE
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 198,000 MILES
I have replaced the A/C compressor; the climate control unit and the A/C compressor clutch will not work unless the relay is jumped. I think it's pins 85 and 30 that are being jumped but I'll have to check to be sure. I know for a fact I'm not getting a ground in pin 85 which I'm guessing activates the ac clutch. Also, the A/C light on the climate control only blinks 3 times when pressed to turn the A/C on. When using a scan tool the A/C can be requested on and it the compressor clutch will engage.
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Tuesday, August 15th, 2023 AT 9:38 AM

6 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
It sounds like the level of refrigerant is low.

here is a video to confirm the issue so you can add and fix the problem:

https://youtu.be/4EqdrBVb0sY

Please go over this guide and get back to us.

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Tuesday, August 15th, 2023 AT 11:35 AM
Tiny
SHON8088
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You think that's what it is? My mechanic said he just recharged the system when he replaced the compressor.
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Tuesday, August 15th, 2023 AT 11:52 AM
Tiny
KEN L
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If the compressor does not kick in the first thing to check is the refrigerant level. You may have a leak/defective compressor.
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Wednesday, August 16th, 2023 AT 11:01 AM
Tiny
SHON8088
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The compressor is new, and the refrigerant was just recharged after the compressor was installed. It was doing this before the compressor was installed but was thinking the same thing you was about the refrigerant being low but that’s not the case.
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Wednesday, August 16th, 2023 AT 11:34 AM
Tiny
SHON8088
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Also, what is weird is that every schematic I look at has pin 87 under pin 30 but in the under the hood fuse box diagram the 87 pin is under pin 86 and pin 85 is under pin 30. The pins 87 and 85 are flipped causing me mass confusion.
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Wednesday, August 16th, 2023 AT 2:23 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
Here are the A/C system wring diagrams so you can see the grounds and fuses that run the system and you can see how the system works. This guide can help you test the connections:

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

Check out the images (below). Please let us know how it goes.
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Thursday, August 17th, 2023 AT 10:13 AM

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