Window down, won't go up...
 

78 300SD (W116), right rear window regulator goes down, won't go up (motor doesn't even click).

Have the regulator out and motor removed, about ready to go back at it and see if I can re-assemble in the up position and leave the switch out just to make sure it doesn't get run down by playful hands again :P.

Any ideas why I can get the motor to run fine down, but not up? Can see that there are only two wires (neither appear to be ground?) going into the motor; tried using the switch from the passenger side door, same results.

Side note, that may well be a red herring: center console switches for the passenger side are basically hollow (on my list parts to replace).

It's an important side note.............

The problem is most assuredly the door switch.

You can confirm by applying 12V to one of the motor leads and ground to the other. The window motor will operate in one direction. Reverse the 12V and ground and the window will operate in the other direction.

Problem is confirmed to be the switch at that point.

Or, just swap rear door switches..............

A broken wire between the door and pillar is a common cause.


Either wire can be ground; depends on the switch position. In the neutral position, system voltage is supplied to both motor terminals. Activating the switch opens one or the other positive circuit and closes that circuit to ground.

A broken wire between the door and pillar is a common cause.

x2

Down works ok on the drivers rear window on my 300TD. Up fails once in a while. I open the door and then use the switch on the door to close the window. I need to fix that one of these days...

If one of the wires is broken, you lose either 12V or ground. The window won't move in either direction.

That would be true for the "door switch to motor" side of the circuit. But those wires don't go through the door. It's not true for the wiring in the other side of the switch. Power to the switch is supplied by two wires; one for up and one for down. If the "up" wire breaks, window only goes down.

I agree.

If one of the wires from the console to the door switch is broken, the symptom will be the same.

I'm pretty sure everyone is wrong and the true fix for this issue is to move to Southern California, then you'll never need to worry about the window being down all the time. :P

The motor has two wires, hook them up one way the motor goes down, hook them up the other way the motor goes up. I'd test this to make sure your motor does or doesn't work. Then proceed with the switches. In my experience most often it's a switch issue, dirty or broken.

It is easy to fix window problem. The fuse is good since window moves. You have the door panel out already then this is what I will do.

1) Check driver side switch and passenger switch. If one is good and other is bad then it is most likely a bad switch. If both do not work then ...

2) Put 12v to motor leads ( only 2 ) and the window should do up or down. Reverse the polarity then the window should go the other direction. This will confirm the motor and the mechanic is OK.

3) Replace the switch with a known good one, either new or from the other side and see whether it works.

4) If all the switches are known good ones then it could be wiring. You need to check for continuity with a meter.

It could be switch, broken wires due to wire fatigue, motor, broken gear etc. It is not rocket science.

Thanks for the suggestions folks - wound up reassembling the window in the up position and driving on home from CT. Will update this thread in the future when I tear open the door and complete the troubleshooting.

Pull and clean the switches in the center console. Amazing how much gunk ends up in there. I clean mine every year or so when I'm bored at my 2nd job. Its easy and makes me feel like a conscientious owner. Last time there was a 2mm X 2mm flake of tobacco in there: rear window would sometimes hesitate, or I would have to push and wiggle the switch. Go very light on the dielectric grease when reassembling: it seems to attract grit.

Just my 2 cents
Scot

Having lived in Southern California since 1955 I am pretty sure after moving to Southern California there will be a need to have working Windows.
I have even seen it Rain and also snow in the Desert out here in CA.

Yes, the Window Motors are not grounded through the Chassis like a Starter Motor is.