Rear defroster not working

Grimor

Original poster
Member
Mar 28, 2013
954
The button for my defroster lights up, fuse 3 in the rear box tests ok. I cleaned the contacts on the glass, but not getting any power to the wires. Does anyone know which side is the + on the glass? and is there a plug in the harness between the fuse and the glass?
 

kickass audio

Member
Aug 25, 2012
955
If you lower the back most part of the headliner you will see a black connector near the dome light. That I believe is the ground wire for it as the local installers who put my remote start in had tapped into that so it could turn on the defroster when it gets really cold out or I command it to turn on from the remote. I believe the left tab is the + part of the circuit and the right side is ground. I cannot confirm this 100% because I will admit, i am too lazy to get outside and get cool to test my output but the wire I was telling you about for where my installer tapped into the wire in the headliner is for - output on my remote start and the wire in the headliner goes over to the passenger side.
 
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AtlWrk

Member
Dec 6, 2011
674
Just fixed mine this weekend (plug had melted at the LGM). If you disconnect the connectors and get +12V between the two then you likely have the same issue I did.

The driver's side connector is +12V, passenger side is ground. Not sure where the ground routes back to in the body but you should be able to test for continuity between the right side connector and any known good ground (FYI, the lift gate latch post and bump stops are NOT a good grounds :tongue: and nothing on the lift gate itself is grounded). Check the left side for +12V to the same ground.
 

Grimor

Original poster
Member
Mar 28, 2013
954
thanks for the info, probably have to wait until this weekend to do some testing.
 

Grimor

Original poster
Member
Mar 28, 2013
954
been a while but just getting back to this. ground and continuity good. i can't find any fuse blown, but none toggle power with the switch either. it's there a relay for the rear defroster some place?
 

DAlastDON

Member
Apr 6, 2014
5,550
Kentucky
Schematic does not show one. The HVAC module sends a data message to the LGM when the rear defrost button is pressed.
 

Grimor

Original poster
Member
Mar 28, 2013
954
DAlastDON said:
Schematic does not show one. The HVAC module sends a data message to the LGM when the rear defrost button is pressed.
I'll check the lgm, my washer line in the back came loose and soaked everything in the door, maybe it shorted something
 

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