PeachParts Mercedes-Benz Forum - View Single Post

JHZR2 · #2 03-14-2010, 10:09 PM

Have you put a multimeter on the terminals of the battery? Do that first. Sounds like a shorted cell to me. The alternator works, and potentially there is enough voltage for some things to happen marginally. The short doesnt dissipate all jumping current, so the car will start. However, once the car is off, the short will dissipate the stored energy in the other cells, and the car wont be able to produce starting current.

What is its voltage after sitting a while? When was it recentlhy checked at sears? what did they do? A battery on an operating alternator will show a voltage that may look OK. Ditto for a recently charged battery, a surface charge may still show an OK voltage for some time.

Next thing I'd do is remove the positive cable and put the multimeter in series with the cable terminal and the battery terminal. Get a reading for how many mA or A youre pulling. If it is over, say, 25-50 mA, then there likely is something shorted in the electrical system. If so, then you need to start using the multimeter in place of fuses to see where the draw is coming from... and track it from there.

Good luck!