Question about 2004 GMC Sierra Denali

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2004 denali rear hvac

Rear heat doesn't work, only cold. I think it could be a flapper stuck somewhere, but don't know where to start looking. Hope it is something simple.

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I had this same problem, With it running and heat and blower on full blast remove and unplug the rear faceplate for the rear heat.
Unplug for about a min.
Shut off engine.
Cycle the key 5 times.
Start engine.
Plug in the plug to the face plate.
For about a min. nothing will happen no heater no blower.
After the multiplex system refinds its address, the rear heat will then work again.
this worked for my 04 trailblazer.

Posted on Jan 21, 2009

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