I am hoping that someone has an idea on the best way to handle the problem of something drawing on the battery of my car overnight. I do not find anything left on such as a light or anything else. There is a motor that stays on for about 60 seconds after I lock the doors. The motor seems to be located on the passenger side of the car's bottom near the front seat. I wonder what motor that might be, and how I might silence it after I lock the door?

But I suspect that the reason that the battery has been drained completely at night is something else. I stopped by an electrical shop earlier, and the owner told me that the problem normally with Mercedes autos is human error, rather than a short, but suggests that I leave the car to be checked out. Before I do that, does anybody have any other ideas? Thank you very much in advance for any help.

Mike Hartigan

Mike:
The motor running may be the central locking vacuum pump, I believe that on a coupe it's under the right side of the rear seat, inside the car. It would make sense given your description. Is the central locking system working OK? Should be locking the gas door and the trunk, make sure they work, and of course both doors. If one isn't working, the motor will try for awhile, then quit trying, this may be what's going on. I doubt it is the cause for the battery to go dead.
This could be many things. Try the trunk light, push down on the probe (with your finger) that is pushed in by closing the trunk and see if the light is actually going out. Make sure there is nothing electrical still on. Are you familiar with the light switch? It must be pointing up to the 12 o'clock position, if you turn it to one of the clicks to the left of "O" (12 o'clock) there is a side marker option that will come on when the key is off, I've had a few roadside calls for this happening. There is a switch on the dash for the rear domelight, make sure that is off. Might be a good idea just to go walk around the car in a dark area, in the garage maybe. Maybe something will be obvious then.
Other than that, I'd say the resting current draw will need to be checked, while pulling fuses one at a time to isolate the problem and go from there.
Oh, are you sure the battery and alternator are good?
Gilly

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Thank you very much, Dan. I am told that the battery is good, after having been tested. I will gladly take your other suggestions, and report here what happened.

Mike:
Sounds good.
Another thought I had is that I always scrutinize aftermarket equipment. Items plugged into the lighter aren't a problem on these as the lighter socket loses power with the ignition off. But look at the battery, make sure there is nothing wired direct to the battery that may be the source, things like radar detectors, cell phones, and stereo equipment can all cause problems.
Gilly

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Gilly, you are the greatest and I thank you. Believe the problem is solved thanks to you. I went to the car, and checked the lights you suggested, including the trunk light. Well, it turns out that about a week ago, I removed the black plastic piece that fits inside the trunk at the back of the car and on top of the bottom of the opening. I was preparing to remove the back bumper of the car in order to install a new bumper strip. I still haven't done this, and have not reinstalled the part. Well, looking at the probe, it turns out that it was intended to press against the black plastic gizmo (non-tech talk) when the trunk was closed. Without the plastic stopper, the probe couldn't be depressed and the light couldn't be shut off! Talk about feeling a little sheepish! Thanks, again.

By the way, I wonder if you have ever removed the back bumper on one of these cars. I loosened the 6 nuts that hold the bumper on the back, but I am having difficulty getting the sides of the bumper detached at the back of the rear wheels. I am afraid to twist them too hard, for fear of breaking the now 11-year-old plastic. Do you happen to know how to detach the sides of the rear bumper? Thanks in advance for any ideas if you have the time to post. Again, I can't thank you enough for the help.

Mike:
"Yep, that'll do it".
I can't remember removing a coupe bumper, I'll bet it's similar to a sedan. You'll have to remove the side trim in the trunk, I believe you'll see fasteners there that hold the side of the bumper to the 1/4 panel, not too hard. Just a few watchamacallits over by the whoozits. Just make sure you don't bend the do-dads.
Gizmo Gilly

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