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A/C heater module in dash stopped lighting up

Tiny
JOHNEAST699
  • MEMBER
  • 1992 CHEVROLET 1500
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
Of course the heater and A/C do not work now. I had an extra module and installed it. No difference. I checked every fuse in the dash fuse box, all good. I seen someone mentioned an LPS fuse. Is it located in the dash fuse box? Any help would be greatly appreciated. TIA
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Monday, December 16th, 2019 AT 12:52 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

Normally, LPS stands for lamps. I attached two pictures below. The first is specific to the control module and the second indicates anything dealing with lamps. Take a look at it and see if it helps. Also, once you confirm the fuse is good, then you need to confirm there is power to the fuse itself (both in and out).

Let me know what you find.

Joe
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Monday, December 16th, 2019 AT 2:52 PM
Tiny
JOHNEAST699
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  • 4 POSTS
I have checked all the fuses in the fuse box. They are all good. Everything that runs off of these fuses is working fine. I am away from my shop, but I will put a test light on each side to be sure. I read some where about moving the main harness under the hood. I did that but seen no changes with the lights. Now the buttons on the module still light up. Just the screen portion that indicates temp variance is not working.
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Tuesday, December 17th, 2019 AT 4:51 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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If we have power to the module, I suspect it may have failed.

Let me know.

Joe
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Tuesday, December 17th, 2019 AT 6:05 PM
Tiny
JOHNEAST699
  • MEMBER
  • 4 POSTS
All power sources are hot. Only one hot wire to the module right? Is there a way to test the module box?
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Thursday, January 2nd, 2020 AT 9:47 AM
Tiny
JOHNEAST699
  • MEMBER
  • 4 POSTS
No inline fuses?
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Thursday, January 2nd, 2020 AT 9:49 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

I checked all through the schematics and there are no inline fuses or fusible links. I checked for a diagnostic flowchart for the module, and found nothing. If it is getting power and won't light but the other things do, then it isn't a ground. The idea that it has power and ground and doesn't light to me indicates it needs replaced.

I wish I had a better answer.

Let me know if you have other questions.

Joe
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Thursday, January 2nd, 2020 AT 10:25 PM

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