W140 S class electric seat fault

[lastyboy]

Hi,
I have a 1996 N Mercedes S420 Coupe. Great car but with 1 small fault.

Intermittently the drivers side electric seat doesnt work at all. It doesnt go up down, forward , recline or anything. The passenger seat works fine at all times.
I will get in it the next day and it will work perfectly, all the functions work perfectly. It will work for 2 weeks , then stop for a couple of hours again.

I spoke to my local Mercedes specialist who said that the switches arent normally a problem and that it might be the electric control unit for the seat. However he said make sure this is the problem before fitting because they are hundreds of pounds.
Ive checked fuses, wiring and everything seems fine. If anybody has any suggestions, i would be tremendously grateful for their help.

 

[television]

If the door switches have PCB's on the rear these can and do go dry jointed, other than that try moving the seat whil giving the ECU a few clouts with a screwdriver handle to see if there are any bad joints in the box, moving the wires will also show up any poor connection

 

[jibcl500]

The seat switches are quiet robust but if someone has removed the switch and plug they can sometimes be difficult to refit so remove the switch first to see if the connection is the problem.

The seat control unit is a common fault on the w140, I think there is also a comfort control unit in the boot on the right hand side, might be worth checking that out also.

Where are you in the UK?

jib

 

[lastyboy]

Thanks for the replies. I ran a test light to the two main wires to the seat. One intermittently lost power and when it did, the seat wouldnt work.

So as a temporary repair, i connected a fuse link to eliminate this fault.

 

[mglb]

I had a similar problem with my sl 129 search this forum under "seat switch repair" hope this helps mark