Good afternoon.
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 upon connection.
- 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 pump operates.)
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,
-marc