Just when I finally have my 1985 190e 2.3 8V running ok, something has gone bad in the electrical system. Something is shorting out and draining the battery in a couple hours. I have not changed any electrical components (ie: Radio, sensors, relays) and have put a new battery in. Any suggestions on where to start looking? Is there a popular component or area that is known to have or cause shorting issues.

The power antenna comes to mind. I would suspect any audio power amps not factory installed, maybe even those factory installed.

To find the problem place an inductive ammeter over the battery cable and start pulling fuses. Look in your wiring diagram for all circuits powered when the key is off and disconnect them. The alternator is one of those circuits that a fuse will not disconnect.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

i dont know the history of you car but make sure it was not a flood car. my car was, but it only flooded to the carpeting i found out after extensive research (that's how i got an sdl for $5000). the cause of the short was the seat modulator under the drivers seat that had gotten wet at one time then corrode(sp?)d thus causing a short.. I replaced it and problem fixed. Car has run terrific ever since and no more problem with seats not working.

try the trunk light. the pin switch may fail leaving the light on all the time.

I've seen it happen before. not sure how common it is though.

Otherwise I would investigate obvious things first, like the antenna steve mentioned.

ALon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon

I have heard of Ashman's trunk light thing before. Perhaps it's a more common problem than I thought.

If you don't happen to have an inductive ammeter as Steve suggested you can use a digital volt meter which may be more readily available. Go to a store like Radio Shack and buy a 1 ohm 10 watt resistor. Remove the negative lead from the battery and connect the resister between the battery terminal and the negative lead. Read across the resister with the voltmeter. Any reading above .05 volts indicates excessive current draw. Continue as Steve suggests with fuses. I might also add that before you go through all this that you have the battery checked by someome who knows batteries. I don't mean someone who sticks a meter on it. I mean have someone do a cell for cell specific gravity test, a load test, etc.You could have a failed battery. I'm not going to call it a bad battery, because I don't feel that disciplinary action is appropriate for batteries. A little humor there.

Good luck,
Peter

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