Do you have a defrost heater in the rear window?
You can grab 12 volts from that, And turn it on and off with the rear defrost switch on the dash!
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2002 Z06
Comp Cam, AntiVenom Intake, Crane Dual Valve Springs, LG Street Series Headers, Hi flow cats, BB Bullet Catback, CPU Tuned, Limo Tint, 150 Wet Shot NX, Hurst Short Throw Shifter. 400rwhp, 520rwhp on spray