When I turn the rear window defroster on in my '88 IROC, the motor dies and the voltage drops to 0. I changed the switch already, so I don't know what else could be wrong. If the hatch is open, the defroster works fine. Can someone please help?!?!

 

Woa.... sounds like one hell of an electrical problem. um i suggest checking your grounds...wow. im stumped

 

Check the hatch struts where they connect at the rear. They have like an insulator where they mount. Maybe the ground isnt correct.

 

ttt

Everything is ok grounds are good. Lift tabs ok.

 

you must have a direct short to ground from either the relay to defroster or the main batt to relay circuits

 

I have this same problem, I was looking today, and the little thingy that goes into the lock (on the hatch) looks as if it's been hitting the lock, making it regular metal showing (the rest looks covered by some coating.) So I was thinking maybe whenever the hatch is closed this is creating a direct ground to the frame, which makes the voltage drop??? My engine doesn't die, but the voltage drops and then goes back up w/out ingaging the rear defrost... Maybe I looked tooooo closely...

 

i figured out what was wrong with my rear defrost. my hatch struts didn't have a plastic coating around the bottom where it connects to the hatch, thus allowing the electrical current to flow through the hatch strut, to the hatch, then grounding through the latch. I fixed it with a little electrical tape (works wonders)

-barry