I have the same issue but the defroster still works, just not the backlight, is your entire button not working?
Sounds like a Fuse or Relay issue.
That rear door isnt getting any power/signal from up front. Mirrors might be on the same "defrost" system.
rear wiper is out also....will check when I get to the lower 48.
Tok Alaska where it's -24 below.:wow:
If both rear defroster, and wiper are not working, it might be the rear window is not completely in the up position. If the sensor for window fully raised is not made, these functions will not work. Try lowering/raising rear window 1st, before looking at fuses.
TechWrench you are smart. In 40 below the rear window was just a smidgen down and once the vehicle warmed up I followed your suggestion and now EVERYTHING works....
thanks man.:hatsoff:
Another tip: If you disconnect the battery for any reason the windows may need to be "reset" by rolling them all the way down then back up. This is necessary for the auto function to work again and it can solve the defrost/wiper issue as well. It never fails to make me feel like a fool when that happens!