Driver side window regulator
 

I have a 92 300D and have replaced the window regulator twice now in 2 weeks, they work great for a few days then do not work at all. The motor still works but window does nothing. I took the door panel off and can see the gears still moving but the window does not move, this has happened twice now. What am I doing wrong?

Maybe the sliding jaw is coming out of the track, you have been in there twice, what are you doing, actually replacing the regulator? Confused on what you have been doing in there, replacing parts or what? Maybe the gear on the motor is worn out?

Yes, replaced the window regulator twice. The gears on the motor are fine, when I take the door panel off I can see the the motor move the gear on the regulator but the arms are not moving. What am I doing wrong?

WOW I have no idea how the gear can move but not the arms, as one of the arms is part of the gear. I can only imagine that you mean the arms move but not the window, in which case the jaw isn't in the track or the stationary jaw is't attached to the door. Wish I could help, maybe one of those things where you have to see it to understand it, can you take a short video and post it to youtube???
Gilly

The only thing that I can think that maybe Im doing wrong is, there is a spring on the regulator, I set it to help the window go up. Maybe its to help the window go down? Set to where the spring tension helps pull down the window? Anyone??

The spring compensates for the weight of the window, so up.
What I don't understand is why you have taken the spring off, never did that.
The arm should be fixed to the gear, if they break off something is wrong.

Rob

No, I did not take the spring off, so I did it right. The spring is to help the window go up, that is what I thought. Then what is going on?

The regulator is defective, the arm that has the gear on it, the arm is spot welded on the gear, when the spot welds fail the gears turn but the arm does not move. I got a genuine Mercedes part on the way. The two window regulators that I have are made in Germany, thought they would be good.

You could weld them back on if they are just loose.
If you can't weld any metal shop can do it for you. If they bother to charge yo for it, it wouldn't be more than $10,-

Rob