Date registered: Dec 2003
Vehicle: 2004 SLK32 AMG
Location: San Diego, CA
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RE: my new 2003, S55 won't hold a battery charge
Was it customer service or the service department at your dealer that told you to run the car every 2 days? I can't believe the service department would tell you that. While it is a bandaid, it isn't a fix and defintely isn't what they should be telling their customers. The service department at your dealer should be able to figure this out...but maybe not as quickly as you'd like. I have had a similar problem with two different makes of vehicles. One was a problem, the other was user error (not mine...)
Auto electrical systems are not fragile. They are, however, becoming more and more complex when you consider all the electronics that have been added. Unfortunately, this does lead to a higher probability of a problem.
It is not likely there is a short circuit. A short circuit would certainly cause other malfunctions.
The most likely cause of your problem is that something is not shutting off or going to sleep when it is supposed to. If this is the case, your dealer should be able to find it within a day or so depending on what it is. Why so long? Because it can take quite a while for the various systems in your car to go to sleep to be eliminated as the problem.
The two problems that I had, one a dealer fixed, one I fixed. One was a glove box light that wouldn't turn off - the switch was not engaging properly. About 6 days later, the car wouldn't start. Took the dealer (not an MB) three days to find this. The other was a vanity light left on but not noticed because all those lights go on when you exit the vehicle. A day or so later and there wasn't enough juice to start the car. I found this one when I got to jump start the car.
There could be other problems. It is possible that the battery is just defective, it happens. That should be easy to test. The charging circuit could be defective and not properly charging the battery.
In any event, your dealer should take care of it as long as it isn 't something like a vanity light or parking light being left on.
Let us know what happens.