The car is a "81 300SD

The back rest will not recline back or go forward on the passenger seat, but everything else works on both seats. If I run a wire from the battery to the grey wire on the backrest motor behind the plug under the seat and before the plug, the backrest goes back through use of the switch. Wire from battery to the orange wire before and after the plug, backrest goes forward through use of the switch. So, the switch is good and the plug is good. I also used a test light on both wires, both side of the plug and it lit up. Why isn't that backrest motor getting power, but everything else is. Oh yeah, I have to figure this out by 7:00 a.m. before my 400 mile trip to L.A. Thanks for your help.

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'81 300SD

It's the switch or one or two wires to the seat at the door hinge.

Orange and grey wires power the motor directly, not through the switch. +12V on one, ground on the other and the motor moves. Swap them and the motor moves in opposite direction. So the Motor works.

Power comes into the switch for all three motors in the seat, and the switches route power accordingly. Since the other motors work, you have power to the switch.

You could have a bad wire in the door hinge area. The constant bending back and forth with the door sometimes causes a wire to fail. I'd expect you'd see this in a driver's door first, but it could happen.

Chances are you have very dirty contacts in the backrest switch that are just not making electrical continuity. There are posts that can tell you how to dismantle and clean the switch. But you don't have that kind of time.

Try this: Move the backrest switch quickly back and forth a couple dozen times with the door closed and the ignition off (i.e., no power to switch). Then open the door or turn on the ignition and try the seat again. If that works for you it will probably be temporary or intermittent at best. Plan to dismantle, clean and remantle the switch at your next opportunity.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

Thanks Micalk,

That's good information to keep on hand for later when I get a chance to take off the door panel. I picked up the switch from a bone yard a while ago and should have tested everything before I put the panel back on. I though that the seat motor might be shot at the time.

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'81 300SD