Just picked up a 1991 560SEL. When trying out all the electrical functions, the Drivers seat would move in all directions, but after trying the forward/backward position, it just stopped working. It makes a noise as though the motor is trying to move it but it doesn't change position. All other positions (tilt, up/down, recline & headrest) still work fine. Any suggestions?

Also, I was checking the rear power seat recline and it again worked, but after setting it to the most upright position, it would not recline again. I hear both motors wirring away, but no movement.

I did a search on the forum, but did not find anything directly applicable. All help appreciated.

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

The rear motor may be due to a broken gear on the slide mechanism. My SDL worked for a long while, then suddenly began jamming up. Gear broke on one side so it no longer engages the pinion on the slide mechanism. They're plastic and 30+ years old...

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Might be that, although I would think the chances of both sides failing at the same time are fairly slim. How easy is it to replace those gears?

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

There is a single motor on the rear seat mechanism. It has cables that run to a plastic gear on each side of the seat to the slide mechanisms. You may have a cable that's come loose, a stripped gear, broken gear, etc. Remove the lower seat cushion (2 10mm bolts at the bottom) and observe the mechanism as you operate the switch. If you see the cables rotating, you know the gears are the fault.

I haven't attempted to repair mine, getting to the gears is easy enough though. I got the mechanism in the upright position and disabled the motor to keep it from getting jammed again.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Several years ago I had the exact problem on my '81 300SD. I removed the seat and alligator clamped the motor to my battery charger. For some unknown reason when I hit the right combination, it magically began moving forward and backward. I put the seat back in the car and it has worked for some ten years.

Am guessing that there was some corrosion in the wiring someplace and the seat removal and testing rubbed off the rust. Otherwise no idea.

So you might try removing the seat and connecting up the motor and trying to run it in all directions. If that does not work, then look for a busted gear.

Thanks guys, I'll give it a try.
Any thoughts on the Drivers Seat issues?

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

Yes , agree with tyl604, same thing happened to me years ago
on a 65 Buick Riviera,that did the trick.
Dervman,when ever you check the power seat next time do it
while your engine is running,it provides more amps to the motors then .
Good luck.

Fixed the Rear Seat recline. Everything was working OK once I removed cables and relocated them. The gears and rack on my car were metal, not plastic and were in good shape. The one side was slightly mis-aligned, which may have caused the initial problem.

With regard to the Drivers Seat, my investigation showed that the motor is trying to turn the cable, but the gear and rack appear to be jammed. Can't see anything physically in the mechanism, but need to check further.

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

The gear that meshes with the rack in the rear seat mechanism is metal. The gear that meshes with the worm on the cable inside the gear reduction is plastic. If the rear seat was misaligned, you probably have a broken plastic gear. Mine would intermittently have issues before it became a constant problem.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]