The rear window de fogger is simply an electric heater. It heats up the glass and water vapor evaporates off.
it doesnt work, it breaks it doesnt work, it breaks it doesnt work, it breaks
why doesnt my heater work on my1985 BMW
Check to make sure your rear window is not down a little bit. I could not get the rear w/s wiper or the rear window defroster to work until I lowered the rear window and then closed it again. Problem solved. Hope it works for you, too !
its probably broken or not plugged in
There is a switch on the dashboard to turn on the rear window defroster (also called a rear window defogger in areas that don't have frost). If you cannot locate the switch, take the vehicle to a local dealer of that product, and someone will be happy to show you where the switch is located. If you locate the switch and the defroster will not work, there is likely a blown fuse or faulty wiring, in which case your local dealer will be even happier to repair it for you - for an appropriate fee.
because it's broke
there is a brake in the contacts on the back window
Could be: Low coolant in the radiator - or - thermostat stuck open - or - heater core plugged.
If the rear window is not fully closed the rear wiper will not operate.
maybe its becuase you have the tank too close to a window or if you have a heater in the tank to high, try moving the tank somewhere from it and see what happens. if not try putting the heater a few degress lower for it, and if that doesnt work either well good luck.
Low coolant? Bad thermostat? Heater core plugged,restricted or airbound? Heater control cable or valve not working?