I suppose that I could wire them to the rear defroster, but that gets too complicated for me. Probably the easiest way, is either to change the thermostat (if possible), or install a small On/Off switch right near the mirror, on the inside of the car.

Actually, now that i know where the thermostat for the mirror is, I am going to blow some hot air from a hair dryer into the mirror assembly. If I am lucky, maybe the heat from the fryer will unstick the thermostat.

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'95 E300 Diesel, 264,000 Miles. [Sold it]