A/C Compressor Not turning on?

Tiny
NHOTSKO
  • MEMBER
  • 1999 DODGE RAM
  • 5.9L
  • 6 CYL
  • TURBO
  • 4WD
  • MANUAL
  • 250,000 MILES
A/C compressor will not engage the clutch. The system is full. I do not have power going to the compressor, only ground. The A/C relay does not click, tried the horn relay and still nothing. Tried jumping 86 and 87 and nothing happens still. I also noticed that both 86 and 85 are grounded and I'm pretty sure 86 is supposed to be power.
Saturday, July 22nd, 2023 AT 10:40 AM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,603 POSTS
Please check for power at the four fuses that run the system. here is a guide to help and the A/C system wiring diagrams so you can see how the system works and which fuses to check:

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

Check out the images (below). Please let us know what happens.

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Saturday, July 22nd, 2023 AT 4:35 PM
Tiny
NHOTSKO
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  • 3 POSTS
Have power at all four fuses.
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Saturday, July 22nd, 2023 AT 4:54 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,603 POSTS
With the key on do you have power at terminal 30 and 86 of the compressor relay?

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Please go over this guide and get back to us.

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Sunday, July 23rd, 2023 AT 2:23 PM
Tiny
NHOTSKO
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  • 3 POSTS
So I have power at 86, but did not have power at 30, however, I ohmed tested from the fuse to terminal 30 and it read opened, popped the fuse box apart and found the wire intact, removed the terminal where the fuse goes, and couldn't see anything obvious but the circuit still tested open, replaced the terminal with a new one and now the circuit reads good and I have power at terminal 30, however, now the 10 amp fuse that feeds terminal 30 keeps blowing.
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Sunday, July 23rd, 2023 AT 4:12 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,603 POSTS
So, this means the compressor clutch has shorted or the wire going the clutch is touching ground, to be sure unplug the compressor and see if the fuse blows.

Here is how to change the compressor out in case you need it:

https://www.2carpros.com/articles/replace-air-conditioner-compressor

and

https://youtu.be/4EqdrBVb0sY

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Monday, July 24th, 2023 AT 11:10 AM

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