Does anyone know if a bad voltage regulator can cause a battery to lose ability to hold charge because it is overcharging??? I am trying to troubleshoot a problem and think that may be what is happening. Here is the story - while driving, electronics started doing weird stuff, like radio coming on and off, tachometer jumping/dropping when I hit the brake, etc. But the car drove ok. Got home shut off car, then it wouldn't restart. Jumped it and it started, but then it died again after driving for 5-10 minutes. This time, ANITLOCK light came on and it wouldn't even crank. I knew this was a symptom of the 10 amp OVP fuse blowing. That was it, but now car will keep blowing the OVP fuse when I replace it. I even tried higher amp fuses and it blows them all. It has done this with 2 different OVP relays so I'm pretty sure it's not the relay. Car will start and run ok for 5-10 minutes, then the ANTILOCK light comes on, I know the OVP fuse has blown, and car dies and won't restart until OVP fuse in replaced. And it has to be jumped to start, because the battery is dead after running for the 5-10 minutes. Alternator/charge light is not coming on. Worse still, after the second time it died, I determined the battery wasn't holding charge so I put in a new battery, and now the same thing happened to it (battery voltage read .10 volts!!!). So I've killed 2 batteries (and about 10 fuses, but those are cheap). I'm hoping this is something simple like voltage regulator. Any help appreciated.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car

Check, or have someone check, the voltage that the alternator is producing. No charge sounds like not enough voltage, possibly regulator, possibly brushes.

You need to measure, not just guess because OVP fuse blows. Sears, Sams, KMart can measure voltage for you if you don't have a meter.

Two dead batteries, unless boiled completely dry, sounds like no charge. They will not be at low voltage if overcharged, they will be at low voltage if undercharged

Low voltage will light up SRS, ABS and other warning lights like a Christmas tree.

Find out what's happening before battery #3 suffers a similar fate.

Best Regards,
Jim

Use a phillips screwdriver and take the VR from the back of the alternator. It would be very obvious if you need new brushes. The VR cost less than $30, if I remember correctly.

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J.H.
'86 300E

This is a typical case of a fauly Voltage regulator in your alternator.
Get a new one from an MB dealer, a Phillips scrwdriver and about 15 minutes of your time
JackD

Update: it was indeed the voltage regulator. Got a new one for $20 from benzbin.com. Put in a 26R series battery from Autozone ($44, plus won a contest for a remote control monster truck while I was there) and the new voltage regulator and car is running great again. Brushes on the original voltage regulator were very, very badly worn down after 90k miles.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car

The brushes mentioned above are 1/2 inch long when new. Yours are likely much shorter due to wear. As mentioned - very easy to check.

It might help to elevate front of car securely. 2 phillips screws on underside of alternator come out and so does the voltage reg. There will be 2 brushes.

Here's what they look like:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog2.mercedesshop.com/&cookieid=1E50U2ODS1E90TK774&year=1987&make=MB&model=300-E-002&category=F&part=Voltage+Regulator