My 87 W250 has power windows. The driver side power window operates fine but the passenger side does not. All buttons operate the motor but the window does not move. Any suggestions?

 

Since the motor runs. If the window is not all the way down it is probably a stripped or broken gear on the motor. If it is all the way down it may be the regulator itself or the motor gear. Either way you have to remove the door panel to look and be sure.