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No communication to rear A/C control module

Tiny
JESS2968
  • MEMBER
  • 2005 CHEVROLET TAHOE
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
Scan tool does not connect to rear A/C control model.
Tuesday, June 7th, 2022 AT 9:29 AM

18 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
There are four fuses that we need to check for power before we replace the rear A/C control module. Here is a guide to help you check the fuses with the fuse identification and locations in the diagrams below:

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

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
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Wednesday, June 8th, 2022 AT 11:27 AM
Tiny
JESS2968
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  • 13 POSTS
All fuses are good.
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Wednesday, June 8th, 2022 AT 1:27 PM
Tiny
KEN L
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  • 48,363 POSTS
Okay, now we can check the grounds. here is a guide to help, you can use a test light but hook it to power instead. Near the quarter panel and rear pillar A.

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

Check out the diagrams (below). Please let us know what you find.
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-1
Thursday, June 9th, 2022 AT 6:45 PM
Tiny
JESS2968
  • MEMBER
  • 13 POSTS
Was checking grounds and unplugged rear A/C blower motor relay and the rear A/C controller was reachable with scan tool and as soon as I plug it back in it is no longer reachable. Is the relay Bad? Or is it something else?
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Friday, June 10th, 2022 AT 1:14 PM
Tiny
KEN L
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Yes, the relay can be shorted which will cause the module to shut down. Good find, also plug the relay in without the motor, if the motor is shorted can cause the same thing. Let me know.
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Saturday, June 11th, 2022 AT 10:01 AM
Tiny
JESS2968
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  • 13 POSTS
Okay, tried that and it was still down. I have ordered a new relay, but it will not be here until the end of the month as my SUV listed above has auto A/C. Does this vehicle have ground splice pack and if so, where are they or the right electrical bus?
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Monday, June 13th, 2022 AT 7:33 AM
Tiny
KEN L
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  • 48,363 POSTS
Yes, the ground for the system is at the right rear quarter panel. Let me know what happens.
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Monday, June 13th, 2022 AT 8:54 AM
Tiny
JESS2968
  • MEMBER
  • 13 POSTS
Just 2 wires?
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Monday, June 13th, 2022 AT 10:18 AM
Tiny
JESS2968
  • MEMBER
  • 13 POSTS
Do you have the wiring diagram for the front upper rear A/C controls?
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Monday, June 13th, 2022 AT 7:22 PM
Tiny
KEN L
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They are included in the wiring diagrams above, which has its own ground as well near the left A pillar. But I noticed the computer data lines headed over to the BCM. Maybe we should try a CAN scan to see if it pulls anything up. Here is a guide and video:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Please run down this guide and report back.
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Tuesday, June 14th, 2022 AT 10:31 AM
Tiny
JESS2968
  • MEMBER
  • 13 POSTS
Unfortunately, my scan tool does not have a can scan.
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Tuesday, June 21st, 2022 AT 8:12 AM
Tiny
KEN L
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  • 48,363 POSTS
Here is one for $30.00:

https://amzn.to/3yx98Cx

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Tuesday, June 21st, 2022 AT 9:13 AM
Tiny
JESS2968
  • MEMBER
  • 13 POSTS
Ordered it, should be here tomorrow.
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Tuesday, June 21st, 2022 AT 1:53 PM
Tiny
KEN L
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Good to know let me know what you find.
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Wednesday, June 22nd, 2022 AT 7:56 AM
Tiny
JESS2968
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Everything appeared to be normal. I'm not sure what I'm looking for, but I did find the issue that the Dorman replacement part is a bad design and does not function like the original part. I found one at a wrecking yard and installed it and it is all functioning properly now.
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Monday, July 11th, 2022 AT 8:45 AM
Tiny
KEN L
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Good work. Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help.
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Monday, July 11th, 2022 AT 2:46 PM
Tiny
JESS2968
  • MEMBER
  • 13 POSTS
Okay, this all started due to my A/C intermittently blowing warm air and would blow cold again if I shut it off for a couple of minutes it would work again. So, I started out by changing the A/C compressor, dryer, rear expansion valve, front orifice tube, both the high- and low-pressure switches and the main control unit in the dash. Now it still intermittently blows warm air for about 30 seconds.
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Tuesday, July 12th, 2022 AT 7:31 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
I'm sorry, we only handle one problem per thread.

Please post your new question here, you must be logged in:

https://www.2carpros.com/questions/new

Cheers, Ken
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Wednesday, July 13th, 2022 AT 11:30 AM

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