wierd window problem
 

1983 300D. My drivers side rear window goes up and down just fine when controlled by the rear window switch, however it does not work with the master switch in front. I check the fuse and it is fine. I replaced that master switch with one I knew to be good and still the same problem. What else should I check?

I would probably do a continuity check between the front switch and the window motor. I think the switches would be in parallel - don't think it's possible to be in series. Maybe there is a broken/ worn/ rubbed wire.

good luck
PMU

Check your wires
 

I had a very similar problem, same window, with my 300SD. Window would go down but not up from the rear switch, and would go up using the front switch only if the door was open all of the way. I had two broken wires that I had to splice around...

Clean the relays in the switch. And quit using the center console as a cup holder :)

take the switch apart and clean the contacts.. i have the same problem and need to try that

Also... i forgot to mention-

Use some di-electric grease (magical jiz as my uncle calls it) on all your fittings. This stuff is amazing if contacts are ok but not great and has solved many problems over time. Also works great when installing new bulbs in my lightbulbeatinge300turbodiesel....

PMU

traced problem to a bad ground. I spliced in a new ground wire to the brown wire on the rear door switch. Problem solved.