Have a 97 PA, 240,000km's on it, and the prob does not always happen. Today it was around -35 with windchill and the rear window would not defrost, along with the other windows in the car, the windshield had some frost on it but was fine. Could not see through any of the other windows. Is it the fuse that is affecting the read window defrost system or something else? It has worked so i know it is not busted...so what could it be...and has anyone else had problems with defrosting windows in really cold weather?

well, you could start by checking it the voltage on the defogger when you thinks its not working..

as for maybe you have too much humudity on the car? is the frost from th inside or out side of the car?

tell us more

Deadring

the frost is on the inside...
how do i check the volate on the defogger?

with a volt meter on each side of the defroster, where the wires plug onto the defogger..you test if you got 12 volts...with the defroster at the ON position of course :)

you put the voltmeter on the DC VOLT mode..

Deadring

If your are getting power to the defogger, but the defogger is not working, inspect the "lines" of the defogger. The lines conduct electricity and act as a heating coil. The usual problem is that these lines get scratched breaking the circuit. If this is the case, parts stores sell an electrically conducting paint repair kit.