My wife's 1987 300E passenger seat has started to baik and fail to respond in some directions using the door mounted controls.
Is this problem most likely in the switch mechanism, relays, or in the motors themselves?
We have owned this MB since new and have been amazed at its reliability, particularly the interior controls and switches.

Any suggestions or links to wiring diagrams will be most welcome.

 

I'm afraid I can't supply any diagrams etc, but it's very likely to be the control switch on the seat. Electric seat / mirror / window switches tend not to be easy to open and fix. I usually buy a working one from a specialist breakers and replace it.

The intermittent nature of the fault suggests it's not the motors themselves.

Good luck!

 

Check to see if you have power at the connector between the wiring harness and the seat. My '95 had a similar problem and it turned out to be a dirty connection. The front of the seat would raise and lower, but the back was stuck down. Use a volt meter while activating the switch...this will tell if the switch is at fault. You can also identify which wire goes to which motor in this way.

 

when was the last time fuses were replaced?