81 300SD. My driver's seat had not been working for 2-3 years. I replaced the switch and it would then move all directions except for front to back - which is what I needed. I removed the seat, turned it upside down on the workbench, and put some jumpers from the motor to my battery charger. It started working front to back for some reason. I wonder if it was not just a little rusty, stuck from not working for so long. So I put the seat back in the car and it has worked ever since - about four months now.

Maybe you will be lucky too.