Hey guys,

first off, awesome forum... I bought my second old diesel a week ago from a friend of mine. It is a 1983 240D with 83K original miles, he was the first owner of it, car is in beautiful shape inside and out. He sold it to me because he did not want to invest the time to figure out alternator issues, he was sold an alternator and it did not work. When I worked on it, the issue turned out to be that the alternator needed adjusting so that the belt would spin properly, a steal for the price of $1500 for that car.

Anyways about the issues....
My rear window defrost switch, when I press it up, the light comes on, then when i take my hand off the switch and it goes back to the middle position the light immediately turns off, anyone know why? Also the lights for those switches (sunroof, rear light, antenna, rear defrost) aren't they supposed to light up when you turn the headlights on? Only the climate wheel light turns on, I cleaned the rheostat as mentioned here and that brought the cluster lights and the window switch lights back to life.

Thanks in advance!

Do these items function properly (sunroof, rear light, antenna, rear defrost) regardless of the lights coming on?

the sunroof opens and closes fine, the antenna works up and down and so does the rear dome light.... they just dont light on when you turn on the headlights...

the rear defrost is weird, I press it up to turn it on and the defrost will light on, take my hand off it and it immediately turns off leading me to believe that its not working right.

I have never had a problem like you describe. I must do some homework. I would think that there is a timer of some sort that determines the length of time the defrost would remain on. Perhaps that timimg element has failed.

Hopefully these will help. Easy to use the search function
New owner, a few questions

Rear Defroster

4 questions '81 240D

It would be more accurate to call it the " Rear Window DeFogger " for the amount of heat they put out does not even approach what I would call an effective "Defrost"er.

Mainly I wanted to recommend you pull one of the connectors from the grid of heater elements... back at the sides of the rear window and then conduct a continuity check to see IF you are even able to getting put electricity through the grid of painted on wires across the window. IF you cannot push electricity across the grid, you are wasteing your time trying to solve what is probably the Defogger relay.