Rear window defroster defogger not working?
 

My rear window defroster not working,the button lights up,but wont defrost?This on a 83 300d.

You may have a defective "combination relay" (N10). The timer circuit in N10 will turn on the light in the switch even though the relay does not send current to the heated rear window. It is possible to remove the relay and take it apart. The relay contacts may simply be dirty/burned. You can clean the contacts with very light sandpaper (gently) and restore the circuit to working.

You should also trace the wire leads to where they connect to the element in the heated rear window. Check the traces with an ohmmeter to make sure you don't have an open element. There are repair kits available although I've never used one.

Those are the two most likely causes.

Jeremy

Another simple test is to chech the heating element on the window for any breaks.
You never know who was throwing stuff back there.

Any breaks can be fixed with conductive "paint". It's actually a paste that comes in a tube much like touch up paint. Can be found at auto parts stores.

Danny

I have an spare relay, not sure if it works or not though.