I was gone for a week on vacation (exactly 10 days of not starting the beast), and when I tried to start it on the eleventh day, the battery was dead as a doornail. I have a new Battery(Less than 5 months old) the alternator is new, and I have no draw on the battery except the clock (Has been verified with a ampmeter). Is it common for the clock to run the battery down in such a short time?


79 300 SD 78K miles

Thats what happend to me once, but the battery was much older. Once you rule out everthing like an external drain, poor alternator, then an internal short is all that it can be. If you can do without your vehicle for a few days, try leaving it sit with a battery cable disconnected. Then reconnect and try to start it. Mine would be dead after 2 days of sitting disconnected.

Gary

Check your battery, I have bought several bad batteries in the past. I had the same problem on my 300cd, and that's how I fixed the problem. I had the same problem happen again, after letting it sit for a month after not being driven for the past few months because of the transmission problem. I also had it happen last week, but this time I forgot I had losened the battery cable, and by reconnecting it solved the problem that time. So what I am trying to say is get your battery tested.

I just returned from 7 weeks out of the country. 82 240D cranked right away and started on first rev--battery was up to snuff. I did nothing at all--just parked the car when I left. I've also stored Benzes over the winter (6 months) without the battery going dead (though I do disconnect the battery then).

The clock can't run down a battery unless it's bad. Check your battery voltage at rest and while the engine is running. If it drops below 12.7 at rest and doesn't climb at least to 13.8 while engine is running, you've got either a bad battery or a bad charging system. A short pulling amperage with the car off could also cause the problem.

I forgot to say that I had my faulty battery tested immediately after driving it to the battery shop. The tech said that the battery, charging, starting systems all checked out OK and that the clock draw was minimal. He said that the only remaining cause of a battery going dead on its own would be an internal short. He said that there is no test for this, just a process of elimination.

I was hospitalized for a month last year, and my spouse used my 240D a few times. She evidently turned on the interior dome (courtesy) light from the dashboard switch, and that was enough to suck the battery dead after a few weeks. I'm referring to the light over the rear windscreen, not the one above the rearview mirror.

Easy to forget it's there and so dim that you don't notice that it's on in bright sunlight, and even at night on my condo's well-lit parking lot its hard to tell whether the dome light is still burning.

Just one more thing to check out.