Mercedes-Benz Forum banner

Battery won't hold a charge!

28K views 15 replies 8 participants last post by  rayq 
#1 ·
I have a 2000 S430 and for some reason my battery will not hold a charge. I have changed my battery 3 times and for some reason if I let it sit for a day or so the battery is completely drained and requires a jump. Yesterday I gave it a jump and it stayed on for about 10 minutes and then when I opened the hood it cut off and would not turn on again unless I jump it. Does anyone know how to solve this problem?
 
#2 ·
It is clearly draining somewhere. A favorite trick is to disconnect the seat adjust motors (if you have them) which seem to develop short-circuits....

Otherwise, it's a bit laborious, but try pulling fuses (in groups) to see what effect that has overnight after you have fully charged your battery. If you are handy with a multimeter, you could check each circuit for its quiescent current.
 
#5 ·
If the battery goes flat and kills the engine after only 10 minutes, Joey is not going to reach a shop to get anything checked out. Maybe it is the hood that is the problem.

He must try to locate where all this juice is going before he leaves home, but he cannot trace electrical faults without a multimeter, and knowledge of how to use it.
 
#14 ·
I brought it to my mechanic and it was the seat control modules that were drawing from the battery making the altenator work harder and resulting in a bad alternator. I have to replace the alternator and the the two front seat control modules. My mechanic says that the control modules cost $800 a piece does that sound correct? My only other option is to disconnect them, but I won't be able to move my seats.
 
#6 ·
A quick thing to check is the ground strap from the chassis to the engine. If that corrodes out or loosens it will cause some strange symptoms, including that your alternator won't put out full voltage. Also, if your battery is drained enough, jumping and letting it run isn't going to get you anywhere (figuratively or literally). You need to pull the battery and fully charge it, then reinstall. While you're doing that you can check the ground strap and clean the terminals/terminal ends since corrosion will impede recharging too.

Once you've got the battery fully charged (I'd actually suggest taking it to a shop and having them charge it and put it on a cyclic load tester to be sure it doesn't have a cell that's going bad, which could account for all of this too) and have checked the rest, then you can start looking for drains.
 
#7 ·
I have an s430 that is draining the battery also. I'm thinkning it s the alternator. But now it states ESP and BAS codes with the abs light on.

I have charged the battery but will not hold the charge for vary long. When I turn on the a/c the battery service light comes on. Any suggestions?
 
#8 ·
Those warnings (abs etc.) come on when system voltage drops too low. Stop driving it or it will strand you.

It could be the battery, alternator or regulator, unless you know your battery is good then have that checked first. There were lots of regulator problems back then so you could change that out or you could replace the alternator since the regulator is part of it (that's the most costly option).
 
#9 ·
my battery died too. Found the right front signal light was on even if the ignition switch is off. It started when I'm getting left signal failure. The rear right park light was ON all the time. I removed all bulbs except the front rt signal. then batt died. I dont know if there is a short somewhere. Need help if this is common when you have bad signal light (LED mirror).
 
#11 ·
alternator removal s430

does anyone know how to remove an alternator from an s430 Mercedes? I have a new battery on it and battery light came on. Not to mention it turns off if I disconnect the battery.

I have removed the fan belt , disconnect battery and removed the electrical connections on the alternator. But having trouble taking it out.
 
#13 ·
I brought it to my mechanic and it was the seat control modules that were drawing from the battery making the altenator work harder and resulting in a bad alternator. I have to replace the alternator and the the two front seat control modules. My mechanic says that the control modules cost $800 a piece does that sound correct? My only other option is to disconnect them, but I won't be able to move my seats.
 
#15 ·
Ok so I had my 2002 S55 at the shop for a little over a month getting rear suspension work and a new suspension accumulator put it. I went to pick it up and it would not start. It was pretty cold out, so the shop jumped the car and I drove it home. I figured since it didn't get driven much then the battery was just not charged to where it needed to be. So I parked it and went to the mountains for about 5 days. Again very cold out. When I came back I went to start the car and the key would not even turn. I bought a 12v portable battery charger and charged it to get it started. Moved it into the garage where it sat over night. Again died again. So now I have had the battery charger on the car for 48 hours. Once I took it off the car was dead again after about 30 minutes. I am not sure how old the battery is as I have had the car for 2 years and have not changed it. I am going to put a new one and see but if the problem continues what are your thoughts. All terminals are clean and connected very well so you know. Thanks for any help I can get.
 
#16 ·
I know this is an ancient thread, but wanted to add some possible insight to the battery drain issues. I was changing my alternator due to bearing noise. My buddy said he had disconnected both battery terminals in the trunk but in fact hadn't so when I was removing the cables from the alternator there was a pretty big spark. I replaced the alternator and battery but the car displayed the same symptoms as the other posts. Turned out to be a blown 150 amp fuse on what is called a pre fuse block underneath the front passenger side carpet. Its pretty easy to access. Mercedes doesn't sell the individual fuses, but they can be purchased online. If you need additional information please let me know. Hope this helps someone solve their problem.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top