I first jumped it with battery, + to +, - to -. Then laid it in the car, connecting power and ground. It doesn't seem to heat up more than a few degrees. Did this w ignore on, and then with the car running. I Google what temp a defroster should reach, 85 deg is what I cam up with. I'm getting mid 60s glass was upper 50's before powering up. Green light on Def sw is illuminated when I turn it on.