HI,I HAVE A 1994 S320 MERCEDES, THE OTHER THE DAY I WENT TO LIFT THE SEAT UP IT MADE A FUNNY NOISE AND AFTERWARDS WOULD NO LONGER LIFT UP FROM THE BACK PART OF THE SEAT. IT STILL SLIDES FORWARD AND BACKWARD AND LIFTS FROM THE FRONT. I UNDERSTAND IT HAS ABOUT 4 MOTORS UNDERNEATH, DOES IT SOUND LIKE ONE OF THE MOTORS IS BAD? ALSO DO I HAVE TO REMOVE THE SEAT FROM THE CAR IN ORDER TO CHECK EACH MOTOR. ALSO THIS IS THE DRIVER SIDE FRONT SEAT.

 

Dry some white lithium grease, this might loosen it up, also try and clean the surface first.