w123 rear left door WINDOW only goes down
 

Hello everyone,

I have a 1982 300D that the rear left door window will only travel in one direction. I have read MANY other posts about similar issues, but have not found one exactly like this. Here’s the rundown of what I have done so far to troubleshoot.
I removed the regulator and motor. I tested the motor to direct 12v it runs smoothly in both directions when the wires are swapped. The motor and regulator are currently not in the door, but I can watch the motor turn in both directions.
When attached, the window motor switch will only work when the “down” is pressed. I removed, dismantled, and cleaned the door switch. I have also swapped out another witch that I know is working in both directions from the right rear door. The effect is the same.
If I manually swap the green and black wires leading from the the switch to the motor, the motor will crank in the opposite direction, but still only when the “down” button is pressed.
I removed and cleaned the console switch. I also swapped out the console switch with another switch and the effect is the same.
All fuses have been recently replaced.

Now i’m stumped. What else could cause this effect?

If it were me.....

I'd check to see if I had continuity in the wires leading from the console to the rear door switch....

Jim

OK, I got this one [SOLVED].
While I am still not entirely sure on the full procedure testing continuity, I was using my multimeter to at least discover what had power going to it. In the course of doing this, I must have tightened a switch that was loose in the center console and now the whole thing works!

I always look at a working door to see how electricity is supposed to flow. The wiring doesn't go bad very often which means the problem is in the switch or motor usually.

I had one window only go down last week and cleaning the Switch cured it. By cleaning I mean I scraped off the balck burnt part to bare metal on the contacts with a pocket knife blade.

Re diagnosis, measure w/ DMM between the 2 motor wires. There is a convenient terminal block inside the door which makes access easy, plus your door card is already off. If you measure <8 V while trying to actuate the "UP" motion, search for the voltage drop. If your front right window shows the same issue, the drop is likely in the fuse contacts.

If using silver fuses instead of gold, this is common. Ditto for sun-roof and other loads. Remove the fuse, sand the ends of both fuse and holder, coat w/ silicone grease and re-install. That fixed many of my similar problems. Someday, I'll have all gold fuses.

As mentioned, could also be a broken wire in the door feed-thru. The window switches can be taken apart fairly simply and sanded of corrosion, but don't fool w/ that until you verify a problem with your DMM. In you don't own a DMM, a trip to HF w/ their coupon will yield a freebie.

On mine the Terminal Block is only on the Front Doors. On the lower bottom.

I had the screws become loose on left terminal block and the window did not function porperly.

The Fues with the ended corroded or burned off look OK till I pulled it out and saw the tip of it and the bracket. 2 Windows diagionally had stopped working.

On mine there is an 8 amp fuse that connects to the Power Window Relay and some other accessories. On mine it is the #12 Fuse and when that is no good none of your Power Winidows work.