what's the difference between this place and MBWorld.org??

anyway... i really need some help.
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Whenever I leave the car idle for 4 successive days, the battery dies and I cant even open the door (need to use the mechanic key)

I tried 2 fully-charged batteries and the result is just the same. It happened 3 times so far.....

I think it's not related to the alternator by logic because

(1) if I dont leave it idle for 4 successive days, no problems at all. I'd been driving the car for more than one month until the first time it could not start after being idle for 4 days.
It implies the alternator is charging the battery.

(2) if the alternator fails, the warning light should turn on.
I tried to disconnect the alternator and the warning light did turn on.

(3) i checked the voltage of the battery during engine run, it read 13.8V so I think the alternator is working.

(4) the battery was fully charged before I installed it.

(5) If everything goes off including the boot-lamp, the amp-meter reads 300mA for the battery.

Someone told me in the technical menu, the std currect should be 50mA.

But I still got a big question.

Even if it's 300ma, the battery has 100A in total. Well assume it's half-full and has only 50A

it should still last 50 / 0.3 = 166 hours or 7 days.

but it just dies in 4 days....

of course, I will get it a service check by MB but any clues?

Add any "Bells & Whistles" ?

no....

the car is second handed... but i think the 1st owner didnt change anything as can be seen by naked eyes.

As you have a current reading at the battery, I assume you have a meter/know how...
So... put the meter in series w/bat feed and start pulling fuses/relays to isolate the system and go from there.

Don't make the mistake of taking an instant reading, as the systems have to power down... [ couple of min should do]

Note * I use a small portable 12v bat from a
power fail/ emergency lighting system to hook up to +/- cables when disconnecting battery to save radio codes/etc....

No clues.. Could be just about anything. (Aftermarket stereo's is often the culprit.)

What i wanted to say was.. That's a really nice piece of car you got there! Beautiful!

Freestyler

__________________
Never criticize someone until you've walked a mile in his shoes. That way, when you do, you're a mile away -and you have his shoes!


'86 300E optically converted to '95 E300 (Sold)
-Blauschwarz on silver
-Black leather
-17" AMG & 15" AMG for winter

After-market alarms are known to cause this sort of problem. The stereo was mentioned and I've read elsewhere that stereo boosters(amps) can also be a problem.

Follow Arthur's advise and use an ammeter to find current draw. If pulling all of the factory fuses under the hood doesn't show a problem, you likely have trouble with something after-market.

For testing, read what Steve Brotherton and Arthur Dalton had to say in this post:

Normal current draw?

Thanks for all your replies and compliments.

Well.... the problem has not been solved....

Last time the engineer tested my current and it read 60mA

Today, I did the test again with my own amp-meter. It is around 60mA/12.5V again (I waited longer this time).

I think it's a very normal reading as the technical menu says normal current drawn is 50mA as far as I know.

I will call MB services tomorrow... but it's very expensive here in HK..... poor me...

I wouldn't expect an MB dealer to be any better at tracing this that your mechanic. If the current draw is only 60ma, then this is less than 6 amp hours over 4 days. As you already said, this is not enough to drain your battery completely.

I would suspect other things. It is possible that your battery is faulty. Even if it appears to accept a full charge, and will start the car OK, it may have an internal fault that causes it to lack its full capacity. Try disconnecting your battery and letting it stand for four days. Reconnect it and see if it has much power left.

I think I'd be trying a brand new, high quality battery before I spent hard earned cash at the dealer.

__________________
Cheers, Neil

Yes, I did try two different batteries. One brand-new 100A, one old 66A. Both completely discharged in 4 days!

The 100A was fully-charged and then left idle for 7 days. Nothing's detected wrong with it.

Really strange!

Can the car suddenly draw very high current during idle for some unknown reason?

Hi goodmanfatfatfat,

Are you using a car alarm? I would think that you checked the current draw without the alarm on. If it draws little without alarm but then looses with alarm, my bet would be the alarm. Can you rigg it so that the alarm is activated while reading the current?

Good luck

Reinhard Kreutzer

Hello,

I had a problem with my battery too (so I tought).
Sometimes the gauge showed me 12V and sometimes 9V or 16V.
Of course when it showed me less than 12V I was unable to start the engine, but when it showed me 12V or more the engine started fine.

I fact it was the regulator (which should be between the generator and the battery) who was out.
Changed this piece and no problem more (keeped the same battery)

Hope this will help.

Regards

Hi Kreutzer,

The alarm is original as far as I know.

Thanks for your tips! The volt-meter, so far, shows 12.5V for all tests. Dont know if it's the same problem but I will discuss with the MB services guy on Thu.

Hi goodman888,

Even if it is the factory alarm and not an aftermarket alarm, it could be faulty. It would be telling what the current draw is with the alarm on.

That alarm circuit might have a leak that is not detected when you read the milliamperes (ma) between the battery and ground because the alarm is off.

Good luck

Reinhard Kreutzer

You mean that when I gauged the battery, the alarm is off?
If so, that explains everything!

Any method to test the current drawn by the alarm.....

You reminded me of that....

the 2nd time (and only the 2nd time) the battery was nearly dead, the alarm was screaming and even I removed the main battery, the alarm was still screaming and I could do nothing but waited until its back-up battery died too.

but it didnt happen for the 1st and 3rd time.