Battery drained overnight - known issue?
The car is a 9/02 build that we've had since 9/03. We haven't gotten any indication of low-battery problems, including when we drove it on Saturday. It fired right up and didn't display any warning lights or malfunction messages. The car was in a closed garage overnight and the outside temperature didn't go below 45 degrees F or so. I took the key out of the car when I parked it last night, closed all the doors, etc. When we went to start it at noon today is was totally dead - didn't respond to the remote opener, didn't respond to the key in the ignitions, trunk opener wouldn't work - had to open the trunk with the metal key and manual release. The battery showed 4.6 volts when I measured it.
Right now I've got a trickle charger on the battery (with the positive lead disconnected) and it's showing that it's charging at the maximum rate (8-amp). Even if I can charge the battery and start the car tomorrow, though, whatever drained the battery overnight will presumably do so again tomorrow. It's going to the dealer, for sure, but is there anything I should be aware of or can do in the interim?
Called MB Road assistance. They sent a dealer truck out to jump battery. Took it in and they diagnosed it as a bad BCM (Battery Control Module) located in the trunk by the spare tire.
They installed a new one and no more trouble.
Called MB Road assistance. They sent a dealer truck out to jump battery. Took it in and they diagnosed it as a bad BCM (Battery Control Module) located in the trunk by the spare tire.
They installed a new one and no more trouble.
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I had the same problem. I would send it to the shop and the problem never went away. I changed 3 new batteries, they diagnosed the whole car and nothing showed up. It kept draining no matter what I changed or did.
However, If the problem is not from your Alternator or any other problem from the car, then have the SBC system checked. Mine didn't have any warning message but my mechanic told me the pressure of the SBC system was low and it needed to be changed. It costs quite a bit. I believe prices will change from region to region. I live in Lebanon, in the Middle east. I was able to buy a used SBC system. So far so good. No more drainage problems.
cheers
The Best of Mercedes & AMG
Last edited by AMGAffalterbach; May 1, 2012 at 11:08 PM.
Please explain what you mean by unpredictable weather? Does the weather have anything to do with the car not starting or the battery draining? I realised that in really cold weather the car wouldnt start, or during any weather change it gets colder, the car will also drain.. How is this possible and whats the cause and solution?
Thanks
Please explain what you mean by unpredictable weather? Does the weather have anything to do with the car not starting or the battery draining? I realised that in really cold weather the car wouldnt start, or during any weather change it gets colder, the car will also drain.. How is this possible and whats the cause and solution?
Thanks
I have never had an issue with a battery or car due to weather, but I know many who have due to plummeting temperatures. This is caused by the battery itself and tends to be a problem in older or malfunctioning units. Solution - load test it at a dealer to verify that it is the problem and replace it.
I have been logging battery voltage twice per day for the past two weeks and have not seen the problem recur. These days many people seem satisfied to hook up their car to a battery maintainer, but I am reluctant to take that path for a car that is driven every day, even if it is short trip driving.
So yes, I have a problem with my battery and no, the dealer has not found a solution. This is a fatal black mark in reliability, in my book.
Larry
I bought a quick disconnect battery terminal and put it on the negative terminal and have been checking the draining every day after work. If it does, I disconnect the battery overnight. The period now is reduced to about a week. I plan to wait until it drains almost all the time before I take it to the shop again. Between now and then, does anyone have a suggestion?
Last edited by TUngpiyakul; Oct 18, 2012 at 12:30 PM.
I am now beyond any rational considerations on this car because the power steering failed shortly after I left town. Two weeks before I had the steering column tilt repaired and 2 months before that both front airmatic struts and brakes rotors all around.
Is there any quick bullet I can shoot here to get this car where I can drive it home if the dealer can't help. IF I have to overnight on the 1200 mile drive and disconnect the battery I have to leave the car unlocked or the alarm will trigger off the secondary battery. I can't even begin to tell my frustration on this car. It has been maintained totally by the MB recommendations for all fluids parts etc and I can't even make a trip from home without stopping in a shop for repairs.
Can anyone offer suggestions? Seat module? Where is it how to unplug to try ? How can I test the battery control module? How about the aux battery relay? I surrender I am having way too many issues on this car.
Can anyone offer suggestions? Seat module? Where is it how to unplug to try ? How can I test the battery control module? How about the aux battery relay? I surrender I am having way too many issues on this car.
Please also share the method of testing seat control module, BCM, relays, etc. with me – pretty, pretty please. I think I know enough to be really dangerous.
For my situation.....I won't lie, I had the dang fogs on. I walked out to a dead (3.2v) battery this morning. Hooked up some jumper cables to the truck and saw the fogs come on immediately, albeit dim. Turned them off and got the car started after a bit of charging.
I hooked up the battery to the battery maintainer for the time being.
Lesson learned.
As a side note, if you google "dead battery mercedes" there are like 2 dozen threads with nothing but people who can't figure out how to use the mechanical key to open the trunk.
I guess I'll check my seat control module next.
I've owned BMWs all my life but this is my first Benz (maybe my last).Dave
2003 E500






