Question regarding power seats for w201 - PeachParts Mercedes-Benz Forum

lsmalley · #1 01-20-2015, 07:53 PM

I just realized that my power seats only function with the door open whether or not car is on or off. Is this how it's supposed to be. I do know there is the contact in the door jamb that opens/closes circuit for the seats, but shouldn't they be functional when the engine is on and the door is closed? I thought about removing the plastic pin so that even when the door is closed the switch is still closed circuit so that the seats are always functional, but this would also drain my battery. Anyone know a way to bypass this or are my seat switches off?

w123fanman · #2 01-20-2015, 11:24 PM

That doesn't sound right. Something in your wiring is screwed up, they should work all the time.

liquiddog · #3 01-23-2015, 12:12 PM

Mine is like is:

running - works open or closed
key on so everything lights up - works open or closed
key out of ignition - only works with door open (strange)

JamesDean · #4 01-23-2015, 03:13 PM

Quote:

Originally Posted by liquiddog

Mine is like is:

running - works open or closed
key on so everything lights up - works open or closed
key out of ignition - only works with door open (strange)

Same here for all my cars.

Mercedes appeared to have this fascination with keeping things off unless absolutely necessary.

liquiddog · #5 01-23-2015, 06:32 PM

The only thing I can think of is they wanted it to work with the car off, but if the switch went bad while the car was off with the door closed and made it go into a "move" mode it wouldn't drain the battery and/or get the seat motor hot.

I wonder what controls that logic?

Zulfiqar · #6 01-28-2015, 04:13 PM

the logic is that you open the door and adjust the seat before you get in and are able to stick the key in the ignition.

However once you are in the car and close the door the system wont work unless you key the car to ON - making sure that there is an actual requirement of adjusting the seat.

tyl604 · #7 01-28-2015, 04:24 PM

After driving my '81SD nearly every day for over thirty years, I assumed the seats worked all the time. However you guys are right. When the door is closed and no key inserted, the seats will not move. I am surprised.

Learn something every day.

MBeige · #8 02-03-2015, 12:48 AM

Additionally if the ignition is off and the door is closed, it can also be a case of the driver stepping away (parking the car). So in that situation there is no need to have electricity to the seat motors.

Merccossie · #9 02-03-2015, 06:51 PM

There is a diode under the drivers side dash that fails and causes this. The seats should work with the door closed. A common failure for sure.

lsmalley · #10 02-03-2015, 06:57 PM

Any info on where or what this diode looks like?

Merccossie · #11 02-03-2015, 06:59 PM

I will post you a pic, a schematic, and the part number tomorrow when I get home.

Merccossie · #12 02-04-2015, 07:24 PM

Here is link with helpful info
Seat Diode - Mercedes-Benz Forum

lsmalley · #13 02-10-2015, 02:10 AM

Could not find diode under the dash....any help on this?

JamesDean · #14 02-10-2015, 09:20 AM

According to mxfrank's post on that link above it looks like its actually under the fuse box panel.

lsmalley · #15 02-11-2015, 06:37 PM

Quote:

Originally Posted by JamesDean

According to mxfrank's post on that link above it looks like its actually under the fuse box panel.

Thanks, JD. I was able to locate it. I tested the diode and the diode is fine. So is there any place else I should check? I tested the amp power draw on my car with everything off except for the normal clock/alarm and I get about .18 - .22 power draw. If I bypass the door check switch for the seats meaning that the seats are always operable, I get about a .43 - .45 power draw. Not sure I wasn't to bypass the door switch so any other ideas?