My right rear on my 124 didn't work when I got the car. The switch was bad so I replaced it. Still didn't work. Took the regulator out with normal blood loss for a Mercedes job(:p ). Worm gear was corroded to the cheap plastic gear and had stripped it out. I swear that thing looked like something from a sunken ship!! IMHO it's a pretty cheezy design for a $45,000 car.