I am working towards pulling my fathers 300 SDL out of 'storage'. It is a sweet car which has some electrical issue that drain's the battery, if it sits for a month. Yet back when it was last on the road I took it to a Dealership to look into the problem, and they said it was "normal"
since then I have stopped going to dealerships for solutions.



Bad Grounds can cause the battery to be pulled down, which is not uncomon. I just dont understand how a 'bad' ground can cause current to flow if the swichs are shut off.

I have disconnected the ground, and attached a test light to it and the battery. it stayed lit indicating a current draw. So I began isolating fuses...

and fuse #2 would blink. Fuse #2 has attached to it: Diagonstic Term. 6, hazard warning system, clock, front roof light, electronic radio, vanity mirror light, electr. illum. control

Also fuse #15 would draw a current, It has: rear roof light, trunk light, safety belt handover arm, swich over valve back seat arrester, central locking system, door lights, reading lamps/rear compartment, aut. antenna, control unit seat adjustment memory.


Oh and the Becker Raido has those Neat ---- in the desplay. does that cause it to play dumb while drawing more current?

How do I take the next step? I am interested in taking on this challange, but I have not any ideas as how to proceed.

Thanks,
Jason

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46 WDX Power Wagon

84 300TDT daily driver

First, get yourself a decent multimeter. connect it inline between the neg post and the battery cable to ground. try to do it with out disrupting the circut if you can. Let me know how much amperage its drawing. On the new MB's anything under 60mA is acceptable, so for an 86, it should be considerably less.

One quick thing to do though, is to verify your trunk light is not staying on with the lid closed, its a common draw problem.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Fuse 2 is probably blinking because the clock is running.
If the door were open Fuse 15 would be drawing current.
Every current draw problem I have ever seen was due to a bad diode in the alternator. The alternator usually would work with the other 5 diodes. But when you disconect the alternator large red wire the load would drop about 500mA.

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Jim
82 300SD saved from scrap yard, 86 front clip,85 500SEL rear end,86 wheels.

John,
I do have a multimeter, although I don't know if it qualifies as 'decent'.
I have checked the trunk light, and it appears to go off as the trunk almost closes. I suppose pulling the lightbulb would help as well..

I will report what I find, although It will not be for at least a week, as work is demanding attention. Thanks for your response.

frankenbenz,
the blinking #2 fuse seemed to be at the cadence of the flasher unit, athough they were not on. Also all doors and such were closed at the time. (summer of 2003, when I played with it last.)

Jason

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46 WDX Power Wagon

84 300TDT daily driver

Oh yeah, John not sure I understand why one would want to connect the multimeter up with out 'disrupting the circut'. is that to observe the flow of current as it is, with out stopping it, and thus incurring a spike when things are connected again?

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46 WDX Power Wagon

84 300TDT daily driver

Shot in the dark:

How long would it take for the clock and alarm to drain the battery. I would be willing to guess that the alarm would probably drain a marginal battery in a month.

Also I replaced my ground cable, the old one was looking pretty tired. For $10 and a few minutes worth of work it isn't a bad idea.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Any aftermarket electronics (alarms, etc)?

No there are no aftermarket electronics, But I am going to go shopping for a digital multimeter, and find out some more information. will report what is found.

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46 WDX Power Wagon

84 300TDT daily driver

There's a good chance it is normal depending on the battery. How do you know you're starting out with a good, fully charged battery? You really need to fully charge the battery and check each cell with a hydrometer. How old is the battery?
Dave

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1986 300SDL

Fuse #15...Trunk light...Have someone get in the trunk...Close it and see if the trunk light stays on....Then let the person out of the trunk....

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83 300CDTurbo 307,000
2005 Honda Element 266,000
56 Nash Ambassador Country Club Special 34,000(under restoration presently)

http://www.peachparts.com/shopforum/car-audio-multimedia/125099-123-install-extreme-dynamat.html

Ok,
New battery installed. test light attached. Multi meter set on 100Ma, which produces a bouncing needle on the meter between 36 and 40 Ma. it bounces by the second, so that must be the clock...

when I attached the test light the reading went down to about 18 Ma with a small flicker, the test light would not glow at all when the multi meter was attached. if everyting was removed, and then the test light would be reattached then it would light up. May be this all means that everything is as it should be?? If so, why has it managed to kill two batteries when it would sit idle? may be I am just skiddish now..

all opinions welcome,
Jason

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46 WDX Power Wagon

84 300TDT daily driver