Bif powell

2002 C32 50k-ish miles. Car cranks, starts, and runs great if I jump it. But the battery will loose all juice over night - it's probably less than 1 year old. Right before this I got a message saying "Light sensor bad" I think it was - definitely something in that realm.

Any trouble-shooting ideas before I take it in?

mdncn2762

I had the same sort of issue except I never got a warning light. My battery would just die after about two days of sitting. I would charge the battery and it was fine for a day or two and then it would be dead again.
I took it to the dealership since I have an extended warranty. At first they thought it was the rear SAM unit, but it wasnt. So eventually they discovered it was the driver seat control module that was inop and drawing power when the car was off. Its been cranking fine for about two months now.

john89011

It's prolly your seat control modules... just disconnect the plugs under your seats and see what happens. Do a search on seat control modules you'll find tons of info. Almost every c32 owner has this issue.

c32used

+1

A member bought two seat control modules from Ebay for $100 that was on another C class car and has a complete DIY of it just do a search I put in in my newbie thread...much luck.

TruTaing

+2... unplug your modules under the seats then jump your car and see if it dies the next morning... just to make sure

AWDman

yep seat modules.

Simbad

worth trying it on with the dealer, i managed to get them to pay the parts for my 03 with no warranty cover. i had to pick up the labor. they are obviously well aware this is a known Merc problem.

Bif powell

Many thanks for the suggestions - I'll jump her and try this in the morning.

I suppose the driver's seat is more likely to be the problem since it's in use more often. One thing I just thought of, I recently started moving the seat up closer than I had before - maybe it a) worked harder to get there b) pinched a wire c) is a Mercedes

So I'll just be able to raise the seat up and see what to disconnect? Then if that's the problem, I replace that box the plugs go right into?

shocker21

Mine just went out last week, it was the passenger side and it wasn't used very often. Sad thing is they wouldn't credit me for the new battery I bought and didn't need.

Simbad

the dealer replaced both sides on mine but it was only the drivers side that had gone, they seemed to suggest it was such a common problem that they should just do them together.

nick 55

The newest part numbers for seat control modules are actually 211 parts. If you change only one, the power seats do not work properly. Replace them in pairs, and any control units with 203 part #s are prone to this current draw issue. New control units should be plug and play. Also best accessed from the back seat, seat moved forward, and up, then unplugged from the front. Good luck with your car. Nick

stef64

I'm having the same problem. Is there any particular year of 211 parts I should ask for so they are sure to be plug-and-play?

cnchung

I disconnected all 3 plugs and the car starts fine now, the battery will die sitting for 2 days before.

stef64

I just spent some time with the car and an amp meter. With the drivers side modual plugged in the car drew 1.9 amps when I closed the door, then it dropped to 1.15 amps after a couple minutes and stayed there for more than ten minutes at which time I was out ao patience. After unpluging the connector closest to the door - the car wanted 1.9 amps when I closed the door, then .66 after a couple minutes, then .02 amps after about four minutes. I went back and forth three times with the same result each time. So, the dirivers seat control modual is obviuosly the problem.

Now I just need to know which one to buy - a replacement 203 model version or upgrade to a 211 model version. I could use some help making this decision.

Of course, for about $3.20 I could put a switch in the power line to the connector I unplugged, and use the switch once a month when I feel like moving the seat. I'm guessing this would be the longest lasting solution.

Bif powell

I unplugged both control modules and the battery held a charge for 2 days now. So I'm going to replace those and see how it works out.

Thanks for all the tips!

c32used

Its funny how alot of us forum members are having the same issues with the seat control modules at about the same time and I am willing to bet that they are all in colder climate mostly...

tonydr00

that happen to me, the seat controller was jammed and was on all night.
found a dime that was jamming it. problem fixed

c32benbrook

So how much does the dealer charge for this? I'm tired of jumping my car everyday, both of mine are bad.

Also, different problem but my left front strut mount is not flushed anymore, I've tried tighten it down more and it won't go flush again? Help, my C32 is in serious help...thanks

doom239

ALL I can say is Check you battery out first. Take it to any parts store and have them load test it, you need to remove the battery for them to do this. If the test fails in any cell Change it.

I have done alot to fix this drain problem in the past. I also a have a DIY for the seat controllers fix on benzword, but it all lead right back to my battery.

c32benbrook

I'll have it rechecked. Took it to autozone and they put it straight on the charger. I could of done that from home. This is my second battery in 2 years. I'll give it another shot thanks doom.