I've never really understood what the demister switch does in my 74 B210.

I can't find nothing in my haynes manual about it, or about the read window defog...

Anyone have answers? I tried wiki, but couldn't find anything.

If your car was fitted with a factory rear demister rear screen it should have a small swith with a blue light on the left hand side of the steering colum. My car never had one but i fitted the rear screen and switch with the wires that were allready in the loom hope this helps

In my car i have the blue switch, but it's up by the fasten belts light on the dash to the right of the steering column (your right)

in my hanyes manual, it's called the demister switch.

I was just curious as it stays on for a while, and shuts off (with the switch still on, light goes out) and comes back on after a while. and my rear window never really defogs that fast.

might have to get out any play around with my multimeter and see where that leads me

Operation is described in the glovebox Owner's Manual.

I think they stay on... voltage to the wires in the rear window. It doesn't cycle on/off. The Factory Service Manual will document it quite nicely.

I'll have to search about to see if i can find it, last i remember the original service manual was in the car when i bought it.

Yeah the light is surposed to stay on on a really cold day it takes about 20 mintues for my back window to clear

Quote:It is not working correctly. Get out the voltmeter and see where the problem is.

Looks like a weekend project for me as well.

-10 this morning when i left for work, frost on the windows. turned the defrost on, was on maybe 10 mins, light went out, smacked the top of my dash light back on, took the full 25 min drive to work this morning to clear my back window, with repeat hitting the dash for the light.

god dam electrical!