triangle12

I recently purchased an 02 C32 and it appears to have the battery drain issue. After looking on this forum, I disconnected both driver & pass seat control modules and no longer a dead battery in the morning. So, if I leave one seat unplugged and plug the other in (then retest battery voltage), would this give me an idea which module is bad? Do I have to replace both regardless? Somewhere on this forum I read you had to replace both even if only one is bad (not sure that's true). The Mazda dealer I purchased from said they repaired the passenger seat (seat didn't move). Guess that doesn't necessarily mean they replaced the module though.
Any opinions? At $150 each I don't want to replace both if one is still good.
Thanks!

insame1

Maybe try a multi meter on the fuse plug one in at a time and see if you get a current draw.

triangle12

Thanks! that's a better idea than plugging it back in and waiting to see if battery drains. As you can tell, electrical is not my area.

kbob999

Here are the instructions for disabling the seat module with key off that I found in the forums. Have not done this (yet), so test your power supply to these wires before cutting anything.

Instructions:

This is to make the seat only operate when the key is on, not when off.
NOTE: This will work on all W203, BUT you may have different colors. Please check the voltage before splicing.

Tools you need:

(2) - Wire Splicers (or soldering kit)
Electrical Tape
Wire Cutter

1) Look under your seat and find the connector with the 3 wires.
(BROWN),(RED WITH GREEN STRIPE),(BLACK WITH WHITE STRIPE) and disconnect it.
The Brown Is Ground
The Red Is +Positive Constant 12v
The Black is +Positive only when key is turned on position 12v

2) Remove some of the electrical tape on the wire loom.

3) Cut the Red wire and Splice it with the Black wire.

4) !!! Make sure you tape off the RED 12v coming in from the connector !!!

5) Wrap everything up with electrical tape and you’re done. Now test. Seat should only operate when the key is on, not when off.

Morphh

I did same mod on both seats for over 1 1/2 years no problems

Khan 55

That's interesting.

Morphh

The only difference is that u can't move the seat without the key in the ignition.

triangle12

Sounds like others have done this mod with success, so I will attempt it this weekend. I have no problem with it only working when I turn the key. Does anyone have a picture? Seems simple but don't want to screw it up.
Thanks!

ez53436

yeap i've unplugged one at a time and left it for a few days to figure out which seat control module was toast. turned out to be my drivers side. i replaced it but left immediately for a couple of months and have not been back yet to test the replacement.

in any case, i highly recommend getting the part through fcp euro. they'll send you the new, oem part literally below mercedes's cost. i have a friend who works at a merc dealership and showed me cost info, so that's how i figured that out.

good luck!

Younis

Please provide pictures on where to cut and splice, I'm new to this and I didn't understand how to do it properly. Thank you

kbob999

Here's the DIY with pics.