Car Doctor Q&A: Could a Dog Be the Cause of a Faulty Defroster?

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You generally don’t know whether things like the defroster have stopped working until you press the button and nothing happens. AAA’s Car Doctor, thinks that maybe this Tahoe owner’s best friend might be the cause of his faulty defroster.

Q. I have a Chevrolet Tahoe and recently the rear window defroster stopped working. The truck is old and I don’t want to put too much money into it. How can I figure out what is wrong and do I need any special tools? I like driving the truck in poor weather conditions and my dog likes the truck, too.

A. The defroster is a relatively simple system, and the only tool you need is a 12 volt test light.

Start with the basics: Did the defrost light come on when you press the button? If no, then the HVAC module likely needs replacement. Connect the test light to the connectors at the ceramic heating grid affixed to the window. If the light doesn’t illuminate look for a broken wire(s) or faulty relay. If the test light illuminates look for an open circuit in the grid itself.

Your dog may be your best friend but may also be the cause of the defroster not working. If your dog scratched the heater grid, the continuity of the circuit could be broken and the defroster won’t work. If you find elements of the grid are broken, you can repair the grid with a DIY kit.

The kits that I have used have a conductive paste that is brushed on to the window grid to restore the open circuit, which generally works quite well.