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87 300 D Turbo, 95 E 300 D, 96 E300 D, 98 E300TD, 00 C230 Compressor, 02 C 320 Wagon, 2010 C300
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Discussion Starter #1 (Edited)
my car drains out the battery over night, I replaced the battery twice, also changed the computers under the driver and passenger seat, disconnected the cd changer and still drains the battery.I did not used for 2 days and now doesn't change gears and "SOS" shows in dashboard. I think is in limp mode.
Please give me advise.
 

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I had a similar problem that was eventually fixed by first disconnecting the passenger power seat and eventually (for loads of money) replacing some seat module. Sorry I'm not scientific here but I was told that some process kept running from the passenger seat, even when the car was off and that drained my battery when the car wasn't parked.
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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2002 C240
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my car drains out the battery over night, I replaced the battery twice, also changed the computers under the driver and passenger seat, disconnected the cd changer and still drains the battery.I did not used for 2 days and now doesn't change gears and "SOS" shows in dashboard. I think is in limp mode.
Please give me advise.
The computers under the driver and passenger seat... Do you mean seat control modules? If you changed them and still drains the bettery..... I am not an expert but I heard the alternator could drain the battery while engine is off. It might be a little difficult to do DIY to check if in fact the alternator is draining the battery while engine is off.

When my car was completely dead, I jump started my car and I had all kinds of warning light (SOS, ESP, SRS, and etc) Then, I replaced the battery all warning lights were gone. Later I found out that driver side seat control module (SCM) and overhead console module (OCM) fan was draining the battery. In fact, the SCM was causing OCM fan to run even if the engine was off and the door was locked. I fixed the SCM as suggested in this forum and it solved the second problem as well. Hope this helps.
 

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2002 C240
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When you disconnect seat control module to check if it drains your battery, make sure to disconnect the power cable connection with three wires (brown, black with yellow strip, and red with yellow strip) not CAN bus cable (the big one). When I disconnected CAN bus cable only, the battery drain didn't stop. Then, I disconnected the power cable only, the drain stopped. Hope this helps!
 

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2003 C320
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The computers under the driver and passenger seat... Do you mean seat control modules? If you changed them and still drains the bettery..... I am not an expert but I heard the alternator could drain the battery while engine is off. It might be a little difficult to do DIY to check if in fact the alternator is draining the battery while engine is off.

When my car was completely dead, I jump started my car and I had all kinds of warning light (SOS, ESP, SRS, and etc) Then, I replaced the battery all warning lights were gone. Later I found out that driver side seat control module (SCM) and overhead console module (OCM) fan was draining the battery. In fact, the SCM was causing OCM fan to run even if the engine was off and the door was locked. I fixed the SCM as suggested in this forum and it solved the second problem as well. Hope this helps.
I know this post is probably a little old but I just had to replace my Alt again because of the it went bad and killed my battery. Turns it it was putting out too much voltage (17v at idle) I'm pretty sure the regulators in these things suck. I would love to crack an old one open and see what goes bad and see if it can be modified to help keep it going. I got just over a year out of my last one. Thank god for Lifetime warranty. :) The "new" one that I got from Kragen (O'riley's now) was a reman. If it goes out again I might just see if I can find a new one for a decent price and see if that helps. It's not that hard to change them it's just that I had to go back 3 times because the "new one" had a different pulley or the back piece on it was different.
 
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