The power seats on my 300SDL stopped working completely. They used to work intermittently but now all functions stopped working, the headrest, the back, and the seat. The passenger side works. I cleaned the contacts on the switch and checked all fuses but that did not fix the problem. I did notice the relay is a bit hot after trying the switch repeatedly. The door light and the door open with key buzzer also do not work. The buzzer does sound when the engine starts briefly. No idea if any of that is related.

I'd start by checking grounds then unbolt the seat and tilt it backward to check the connections. I know it's a painful to remove seat bolts without the seat functions to provide space but that's the ticket.

I'm doubting that all the functions quit working at the same time due to all the motors failing so the problem is certainly electrical. Can you switch the relay with another to see if that's the issue?

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84 300SD
85 380SE
83 528e
95 318ic

Open the door, pull out the bellows where the wiring is, look for the broken wires... fix them.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Did you figure out the messed up wire yet?

I pushed my body into the seat pretty hard and they started working again, i guess something got hung up.