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2002 ML320
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247 Posts
Discussion Starter #1
The wife went to start the ML this morning and nothing. I jumped it and it started right up and ran okay. I looked for a light that got left on and would have killed the battery but couldn't find anything. I drove it to work, parked it and the ML's dead again. Now, the original battery was replaced with a new Bosch battery about 3 months ago. Do you think I got a bad battery that just refuses to take a charge or could it be something else like the alternator? 2002, ML320, 103K miles. Thanks for the thoughts.
 

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99 ML430 - 13 328i
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1,112 Posts
i think somewhere someone replied something about the voltage regulator in the alternator. that part, if it fails, does not give charge to the battery. but i could be anything.
 

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2001 ML430, 1983 300SD, 2008 GL450
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904 Posts
The causes are usually one of three things: Corrosion on the battery connectors, alternator (usually the voltage regulator), or a loose wiring connection somewhere. The fixes are all fairly simple but finding out which one it is can take some time.

Budget two hours of time for just diagnosing the problem.

Another nice design on these vehicles is that the voltage regulator is easily replaceable. Most of the time a "bad alternator" is merely a bad diode or transistor. In older cars these items were relatively easy to access but sometime in the late 70's manufacturers started designing alternators so that they were not repairable and so you had to purchase a new alternator.
 
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