ok I`m working on a 1981 300SD . I have 12v to the plug under the seat coming from the switch. when I put 12v to the other side of the plug with my jump pack the seat moves . when I plug them in together nothing. anyone have any ideas ? is the seat not grounded by the bolts in the floor? Thank`s Rick

I suffered through repairing one of these on my '82 300SD.
ASSUME NOTHING!!!

Someone had reversed some of the terminlas in the seat switch on the door. I had forward and back, but the part of the switch for recline was dead. I rebuilt, and cleaned that switch several times. I forget how I discovered that someone had reversed some of the wires at the plug, but once I got them right, it worked fine.
Check continuity from switch to seat connector for each wire. Then check that each wire is really where it belongs.
I repeat--ASSUME NOTHING

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1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags

12v is just voltage, it sounds like there is no AMPS flowing to the motor. Check all your plug connections for corrosion, loose connectors, partially broken wires, and possibly a bad switch.

the switch is brand new but I didn`t install it. my friend that i bought the car from did. I`ll check that out. I was thinking if i had power to the plug it should work. thank`s a lot I`ll check that out tommorrow