Yes, the original post was for a 560. My 85 300SD has a cable similar to a speedo cable from the motor to the gear mechanism on the left only mounted bar assembly for the power headrest. The cable has a square end on the gear side so is easily removable for testing. Once removed, you should be able to trigger the switch and then see if the motor moves. If it does, the culprit could be stuck/jammed/dry etc headrest mounts to vertical mounts on the back of the seat itself. That was my problem on my 85 300SD that I fixed yesterday. Not sure what the other seats look like inside but worked for mine. Just trying to help others in the same position troubleshoot the problem.