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2003 Mercedes Benz S430 Electrical load while stored

Tiny
ROSS PARKER
  • MEMBER
  • 2003 MERCEDES BENZ S430
  • V8
  • 2WD
  • AUTOMATIC
  • 50,000 MILES
Hi. We recently purchased a used, well maintained 2003 MB S430.
A new battery was put in the car in Nov '08 just before we bought it.
The battery has gone dead 3 times over the past 4 months, after leaving it stored for just 2 or 3 weeks!
Our "general mechanic" checked the draw when everything is turned off, and found no short nor exceptionally high draw of the battery.
He suggests we should use a trickle charger of some type, but, that just seems inconvenient.
He suggested this is common for these models. Is it?
Can I remove a fuse on a circuit that has a large draw that doesn't require resetting information, and doesn't control a system that's important when the car is stored?

updated3-20/09
you didn’t answer my question. It was “is this type of problem typical of these models"? And/or “can I remove a fuse on a circuit that has a large draw that doesn’t require resetting information?". The 2nd question is most important. Thanks. Ross
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Tuesday, March 10th, 2009 AT 2:00 PM

8 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
If your mechanic checked for full voltage draw on the battery with key off, and found none. Then that rules out battery drain. I have had brand new batteries off the shelf where they would start the car every morning, start to go home at night, day after day, no problem. BUT, if you left the interior lights on for 15 to 20 minuets or let the vehicle sit for 3 or 4 days, the battery was dead. Bad battery. I would have your battery checked. Let us know what you find.
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Tuesday, March 10th, 2009 AT 3:35 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
I'm a little confused here. I don't know who "Mike " is or what he told you. Can you fill me in?
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Friday, March 20th, 2009 AT 3:44 PM
Tiny
ROSS PARKER
  • MEMBER
  • 4 POSTS
Hi James. Mike was an admin guy at your end who just told me how to respond to you.

My question was not answered. Is this problem common to these models? And can I remove a fuse on a circuit that has a large draw but doesn't require alot of resetting/reprogramming when I put the fuse back in?
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Wednesday, March 25th, 2009 AT 1:33 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
According to the TSBs, this is not a common problem. In reading your previous post, you mechanic stated he could find no full voltage draw. Is this correct? Please advise. The proceedure for finding a full voltage draw requires pulling fuses one at a time until you pinpoint the source of the draw. Usually, in doing this, you will lose part or all of your stored memory.
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Friday, March 27th, 2009 AT 1:25 AM
Tiny
ROSS PARKER
  • MEMBER
  • 4 POSTS
Hi James. He did say that he found only normal draw off the battery with the key off. I beleive what he did was assess the current draw with an ammeter that encircled the +ve battery cable. I beleive he did not remove any fuses.

It sounds like you're going to recommend doing the test as you suggest. By removing one fuse at a time and measuring the draw across the fuse's contacts with a milli-ammeter. If so, please tell me what milli-amp number is too high, to indicate the circuit that has a problematic draw. Thanks, James. Ross
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Friday, March 27th, 2009 AT 4:51 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
Ross, If you had a full voltage draw on your battery that drained it overnight or in a couple days s clamp-on amp meter would probably pick it up. But, if it takes 2-3 weeks, it's not going to. It only takes 5 volts to keep the memories alive in the ECM, radio, seat position, alarm, etc.
If you are absolutely, positively sure your battery is good and want to do the load test yourself, I can give you the steps. But, you will lose your stored memories. Let me know what you decide.
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Sunday, March 29th, 2009 AT 12:08 AM
Tiny
ROSS PARKER
  • MEMBER
  • 4 POSTS
Yes, please James. Please give me the steps for me to do a load test to find the circuit that is drawing down the battery. Ross
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Tuesday, April 7th, 2009 AT 9:56 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
OK, to start, let's try to save the accesory memories. You need to run a jumper of a type from the - negative battery post to a ground. Any size insulated wire will do. But, you need to do it in such a way that you can still remove the negative battery cable from the battery. Once you remove the negative cable, the jumper new jumper you installed is what's keeping the various memories ie; radio, alarm system, seatadjustment etc, alive.
Next, you will connect an ordinary "incandescent" test light, not a neon or led, the same way as you ran the "jumper" wire. An old style tail light (#1156)bulb with a couple of wires soldered to it works great.
When you get one end of the test light connected to the negative term of the battery, touch the other wire from the test light to the positive term of the battery. Make a mental note of how bright the test bulb is. Now, ground that end of the light wire to a ground source like you did the "jumper" wire.
My computer is locking up. I need to back out and re-enter your post. Bear with me.
There, that's better.
Now that you have your test light attached, disconnect one end of the "jumper" wire and allow the test light to work in it's place.
Is the test light as bright as it was when you touched it to the positive battery post? Or is it just a glow? If it's just a glow, not as bright as before, you don't have a "full voltage draw". You have a battery problem. Let me know. And we'll go to plan B.
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Wednesday, April 8th, 2009 AT 1:38 AM

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