Rear window stuck open
 

I was trying to roll up the right rear window in my '78 300D and instead it decided to just roll all the way down. The control switch under the actual window doesn't work and the one up front breaks when I press it and blows the fuse because the little metal pieces inside touch. Because of this dilemma, I would prefer to bypass the broken switch system altogether and maybe touch whatever wires together I need to get the window moving.

Between the driver's side front and rear window switches is the child lockout switch which when activated prevents the rear windows from being operated by the switches in the rear doors. You might double check that child lockout switch to see if it is activated preventing the rear window switches in the doors from operating the rear windows.

If that doesn't help the window motor is powered by a pair of wires one black and one green, you might be able to access them at the switch in the rear door but if not you can take off that door's inner covering and there is a connection block for the window motor that has the green and black wires at it, you could separate that connection and apply power to those wires and operate the window to get it closed. Good luck!

Toggling the child lock doesn't seem to make a difference. I saw sparks when I tried to put the window up with the control switch open. Some of the wiring up front might be mixed up because the front passenger switch wires aren't connected to a module like the rest. I found the black and green wires on the door, but the ones connected up front are different colors. I have an 18V drill battery I plan to use if I can just find the right wires...

When I did mine I removed the rear Door Panel to get at the Motor Wires.

If you do that you need to remove the Plastic Shield that in the Pocket where you stick your fingers to Pull the door Lever. After that there is 1 tiny screw. I mention this so you won't yank on the Panel.

The rest of the Door Panel stuff is obvious.

Also the Window Motors are not grounded though the Farme/Body of the Car like a Starter Motor is.

Already got the door panel off, but it does me no good since the window controls on the door aren't working.

You don't need the window switch in the door, open up the plastic connector shell that the door switch plugs into, then remove the green and black wires and there female connectors from the plastic connector shell, these two wires go to the window regulator motor. Apply 12 volts to these two wires, the window should move up or down if the electric motor works, if you want the window to move in the opposite direction, reverse the polarity of the 12 volt connections to the green and black wires.

Your rear switch probably is not bad. IIRC it gets its power from the consol switch for some reason.

you could unplug the harness from the rear switch and put it on the front switch temporarily to get the window up.

Cool beans. Connected the motor wires to the drill battery and the window went right up. Just in time because it's supposed to rain tonight.

Hahaha yes! This helped me out so much. My front passenger window was stuck closed. I just got two audio connectors with wires, plugged them into the green and black connectors on the front switch and got the window up!

Thanks a million, now I don't mind waiting so long for that new window switch to arrive.

The window switches, can be taken apart and cleaned....There is usually no need to buy new, unless the chrome is flaking of the first style or the icons on the second style are worn off...

Thanks for the Audio Connector tip. Nice to know what fits/plugs into the sockets.

Does not sound like the below was your issue.
On the front doors of a W123 there is a wire terminal block bottom front. The screws on mine came loose and My window on that side stopped working. Tightening the screws fixed it.
It is a good place to access the Widow Motor Wires on the front.

The window switch would roll the window down, but wouldn't roll it back up. I took apart the switch to try and repair it, but it looked like on of the contacts was completely worn down when compared to the other three.

Anyways one new switch was only ten bucks so no big deal, I'm just glad I was finally able to get the window back up.