The rear defroster in my girlfriends 2000 Olds Alero no longer works.
The light on the button comes on, but nothing happens out back.
All of the fuses in the dash and under the hood are okay. The relay
was swapped out with an identical one from another circuit... like
the blower motor or something. No go.
Testing the voltage on the leads, is where things get weird. In all
tests, the car was running and the defroster button was lit:
- Leads disconnected. Attach volt meter. I see about 13 volts.
- Attach leads to heating grid, the voltage drops to 0 with a tiny spark
- Disconnect leads from window, and I can watch the voltage rather
slowly climb back up to ~13v. (About the speed the counter on a gas
So from what I'm gathering here, it "looks" like some sort of a
capacitive circuit is tied into the defroster.
The only thing that has changed with the car, since the last time the
defroster was operated (approximately last spring or so), was that the
blower motor fan/speed control on the dash was not operating correctly.
A shop replaced a resistor up under the dash. I forget the exact name
right now. Was it a balast resistor?
Is there more to the defroster circuit than just a button tripping a
relay to power the heating element?
Should I dig into the dash, to make sure everything conected securely
behind the temp-control section?
Any other idea's where I can stick my hands?
Thanks for your time,