Hi All, I have a 2003 E200 which recently developed a problem. It completely drains the battery every so often, at random intervals. And I mean "drains it" !!! not even enough to open the doors left in it. I have to open the boot door with the key and take out the battery and charge it. At first it gave notice af a "malfunction" and turned off all electrical consumers, but now it just goes stone dead overnight. I thought the battery was on the way out and replaced it but after a few weeks it happened again, and always when the wife is going somewhere, so I keep getting it in the neck LOL
I would be grateful for any suggestions,
Cheers,
HV

 

funny, I had the same problem with my 96 E300D, found the trunk light stayed on with trunk closed. It is a bitch to find the cause if it is intermittent. A DC current tong tester
can help. place it over the battery cable and read the Amps when all the doors are close and the car is locked and resting.
In my case the car is also not used often enough so I installed (permanently) a small 2A battery charger (automatic type) and leave it plugged in. The charger plug hangs down outside of the hood, so no need to open it.

 

I had the same thing happen on my 96e320. It turned out to be a bad switch on the driver door. Eventhough I would lock the car the lights that are at the bottom of the door would stay on and that would drain the battery. Lock your car and look inside towards the bottom of the doors to see if you see any lights on, if so one of the door switches is bad or loose. Hope this helps..