Power Seat Backrest Problem
Thread Starter
Junior Member
Joined: Feb 2005
Posts: 19
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Power Seat Backrest Problem
I have two W126 cars. On my 300SD neither of the back rests adjust when you move the switch. I didn't really care about it though on my old Diesel. But on my 500SE AMG the passenger side backrest will not adjust. It has a brand new switch on the door too. The drivers side works. I tried almost everything. I took out the seat and gave power to the motor with a battery and the motor moved and the backrest adjusted, so it's not the motor. I tested the wire for continuity from the switch to the plug under the seat, and it does have continuity. So the wiring isn't bad. Theres no problem with the fuses. I don't know what else it could be, maybe a bad ground? If anybody has had the same problem or knows how I can fix this it'd be greatly appreciated.
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Joined: Apr 2005
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Just because it has continuity, it doesn't mean there isn't a short somewhere. Try partially plugging in the connector so that it has contact with the the pins and the metal still shows. Then connect a voltmeter while actuating the switch. See if they are hot where they are supposed to be. It is possible that the new switch you bought has a defect. If not, then you will probably have to replace the wiring.
Thread Starter
Junior Member
Joined: Feb 2005
Posts: 19
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I just tried what you suggested. I bought a new switch and tested it and it still wouldn't work. I checked if the wiring was good through the door. Each wire for the backrest shows 12v going through when I activate the switch. I took the seat out and gave power directly to the plug from a car battery and the backrest moved. All the wires are going to the right places on the switch according to the diagram. The bottom of the seat can be adjusted no problem. This car is euro, I don't think their would be a difference in the switch though because the part number is the same. The door used to have a solder point switch but it was missing the pegs to adjust the seat, so I replaced it with this plug switch. If anybody can help me out, that'd be sweet.
Newbie
Joined: Apr 2005
Posts: 24
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Well sounds like there is a break/short somewhere in the path from the door to the actuator on the motor. If it were me, I would buy a quality spool of wire and rerun it all the way through. It will take an afternoon to do, but will be sure to fix it. Good luck.
