I know there is some sort of a drain on my E, but I have been unable to pinpoint it to date. Our '99 E300 has virtually ZERO drain on the battery. We've had that car parked in the garage before for a few months, and it fired right up upon first start. My '97 will barely start after only sitting a week. It would be nice to figure this out.

Both have a good battery, and as of recently I have replaced my battery with a new Interstate unit and currently maintaining the charge with a Yuasa 1.5amp trickle charger. And yes, it is the correct battery under the rear seat.

Curious if anyone else has had this type of issue, and hopefully been able to figure it out.

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#dieselFLEET
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'97 E300
'99 E300

1.'Guess what it is,yourself (And get Lucky) [Alternator Diode(s) Bad?,Glow Relay?,Etc.]
2.'Drag out the old Multimeter and start testing.
3.'Kiss the Savings Account and your IRA Bye,Bye and drag it to the Dealer.

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'84 300SD sold
124.128

Well, I've already replaced the alternator a few years back, so 1 is crossed off the list.

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#dieselFLEET
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'97 E300
'99 E300

Didn't 97s have the biodegradable wiring harnesses? One of my cars had the same problem with batteries going dead in a few weeks. Also failing o2 sensors. Took me years to discover the bad spot in the wiring harness. There were no outward signs. Just a slow power drain.

Good luck

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1979 240D, 4spd manual, Power Sunroof, manual windows, 147k miles, Pastel gray/Black MB Tex.
1991 300D 2.5 - Smokes like it's on Crack!

Those harnesses from what I recall should have been phased out by '95 MY. I've had the same constant drain ever since I bought the car in '02. It wasn't an issue when I would drive it everyday, but now it's a garage queen, and every so often I find some pockets of time to try and tackle the little things that have bothered me.

Currently, still working on the suspension overhaul. It's been an on going, learning curve for over 2 years now :-) Hopefully soon it'll all come to an end.

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#dieselFLEET
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'97 E300
'99 E300

New parts don't necessarily = properly working parts. Try isolating the affected circuit connecting an ammeter between the neg battery post and terminal. Pull fuses until the drain goes away to determint what circuit. Next reinstall fuse and begin disconnecting loads. Expect the problem to be a at the end of circuit or connector. Lots of info available. Google parasitic drain. Here's a start. http://autorepair.about.com/library/images/bl901lib.htm

And remember that your car has three fuse panels. Find all of them and you're halfway there.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Just put an ammeter in the main line to the battery when the key is off and all of the lights are out and see what the standby current draw is...it should be near zero. If it is then I would look to the charging circuit.

If there is some draw like 100ma or more drawing at standby then start pulling fuses out until it drops off and then you will know what circuit it is that is draining it. From that point you can pinpoint what device on that circuit is the culprit.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Thanks Guys for the tips!

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#dieselFLEET
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'97 E300
'99 E300