Battery/Alternator light - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 12-05-2007, 01:54 AM Thread Starter
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Question Battery/Alternator light

I have a C200K Sport Coupe (2002) and recently the battery/alternator light comes on and off intermitently. My garage says they can't find anything wrong with the belt or tensioner and to run it till the light comes on permanently. Anyone else have/had the same problem and what was the resolution.
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post #2 of 4 (permalink) Old 12-05-2007, 01:57 AM
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usually the alternator will intermittently fail on the car. try first by replacing the voltage regulator
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post #3 of 4 (permalink) Old 12-05-2007, 06:11 AM
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The alternator has carbon brushes in it that run against the armature. The entire assembly is held on to the rear of the alternator by two screws. You might want to remove the plug that connects the alternator to the circuit (also on the rear of the alternator) and then remove the assembly with the brushes, transistor, etc. Take a look at the brushes to see if they are shot. Sometimes they are jammed up with carbon and road dirt, etc. Blow out the assembly with air and see if the brushes move freely in and out. You might want to stretch the spring that loads the brushes outward because if the brush is low on spring pressure and worn significantly, it won't reach the armature with any real pressure and cause an intermittent connection and the problem you are having. The long term fix is to replace the brush assembly or to have the alternator rebuilt. Good luck

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post #4 of 4 (permalink) Old 12-05-2007, 03:12 PM
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The brushes tuttebenne mentions are part of the voltage regulator assembly, under $100 but you have to know if you have the valeo or bosch unit -- at least in the US market. In the US there was a voltage regulator recall that spanned a few years and a few models (although not all by any means), since you're in Europe (I'd guess based on the engine) you'd have to see if it is in effect over there. (While we're on the subject, please update your BW profile re: vehicle and location, that information can be quite useful.)

If you're in the DIY mindset you'd want to disconnect the battery before you go pulling the alternator or the regulator.

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