I have a 1993 300D 2.5 Turbo. The front drivers side window works fine going down. Going up, it hits the top of the door frame, at the fully closed position and then thump, thump, thump. The motor should stop, but, it tries to keep going up. I lift my finger off the close button and it stops fine, but, I'm worried that the window will break or the motor or some other part will be damaged if I keep using it. It seems like the 'limit switch' is not engaging at the right point, or some tab or maybe gear tooth is broken? I'm trying to figure out where the 'limit switches' are that tell the window motor that the window is fully closed or fully open. Thank you, Richard

Most power windows don't have any limit sw, the motor stopping is everything being run to a bind and the motor stalling. The same goes for one touch express down, when the controller sees the current go high it shuts off power. ( Low rent systems use what amounts to a thermal circuit breaker in the switch. ) It is good practice to let off the button just as the window hits top or bottom.

Your car may or may not have any sort of limit sw but I really doubt it has one. The thumping is likely the motor gear slipping on the window regulator. The window regulator has a 1/3 of a gear on it and the teeth on the up portion are probably worn out or the motor has worked lose from the regulator.