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Discussion Starter #1
I have a 2002 C240, and my battery goes dead in 1 or 2 days. When jump starting the car the car runs fine and I have no-warning light on.

I called MB Road Side Assistance and he tested the battery ad said you have a good battery, but you have a battery drain issue. Then he tested current draw when car was off and said: there is a 130 MA draw. He said on C240 current draw should be less than 60-70 MA.
I have unplugged both power seat modules, and again no change.

I would really appreciate any advice on how to resolve this issue.
 

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2004 C230 Kompressor Sport Coupe
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1,903 Posts
Start pulling fuses one at a time with an ammeter on until you find the drain. That's all there is to it. Then you know what system to investigate.
 

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Discussion Starter #3
I have checked the overhead light module and all the controls work properly i.e: the dome lights front and rear, Tele-aid, and the power sliding roof.

However, today I notice the noise is coming from the overhead light module, where there is a small fan which pull cabin air in to sample for air temperature (part of your climate control system), and the humming noise is coming from the motor which suppose to shut off in about 12 seconds after you turn off ignition and all the doors are lucked.

I put a small piece of newspaper over the motor and it stayed there and I can hear it running even though the ignition is turn-off & all doors are lucked.

What could cause it not to shutoff? This issue is draining the battery when the car is turned off. I would appreciate any comment in how to fix this issue.
 

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2001 C320 Black/Tan
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I had the same problem except that I had a 320 instead of a 240, but this is not an engine issue.

If you have power seats then its the senors that control the seats. They will prob draw around 2 amps each. My battery would drain over night. I thought it was a battery at first. so i replaced the battery. then one shop told me it was the alternator. so i replaced the alternator. still had the problem. finally MB told me that it was the senors so i had to pay up big AGAIN.

Two solutions.

You can replace the sensors and with labor it will cost you around $1200-1300 (tahts what i did because i want to use the seat function)

OR

You can disconnect the sensors underneath the seats. If you do this the draw will stop and your battery will not drain. The downside is that you will not be able to adjust your seats, so if you do this make sure you set your sets to the way you like it.

other than that,there really is no solution. its one of those things that mb knows about but wont recall.
 

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On the c class, the most common thing to drain the battery is the seat control modules. Unplug them under the front seats and see if they go away.
 

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he stated that he did unplug both seat modules, obv this is an old thread, but I am running into the same problem now and was just searching for a possible solution..
 

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2002 c240
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Any body to help ! I jump start my C240 twice in a week already, it runs fine but when i tun of the engine the parking light goes on and off on its own and that is draining the battery.Is this the battery problem?? or Sensors?
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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How old is your battery? A weak battery can cause all sorts of strange things to happens, like the lights acting oddly. If your battery is showing below 12.6v at rest, 11v during cranking, and 14v at idle, then I'd check it and the alternator.
 

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I have the same issue, have pulled all fuse(but didn't pull relays) yet same battery drain, I have changed battery, yet still getting 0.96A drain on battery, I have pulled the seat adjustment cable yet to no avail.
 

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2006 c230
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Same as above, issues with power drain and no fuse removal or unplugging of seat controls changes the drain. I read it could be related to outside Temp sensor being bad or BCM ie says its 185 degrees out side. I ended up hooking up a pwr disconnect switch under the hood mounted close to the battery, a hassel but less than jumping a dead battery.
 
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