Charging system problem - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 09-21-2008, 07:46 PM Thread Starter
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Charging system problem

This is on a 1995 E300D automatic transmission

While driving the other night my radio started to cut out and the dash lights were getting dim. I first thought that the serpentine belt had come off or had broken. The belt was there and apparently in good order. I checked the voltage at the battery and it was low, about 10.8 volts, I was surprised everything was still working. It was late and I had to go to work the next morning so I bought a marine type starting/ deep cycle battery (something that could take the discharge cycles) I thought it was the alternator. I took the alternator off and took it in to a parts house, they put it on their alternator test machine and everything tested fine (voltage, diodes, regulator, etc) I did notice that the battery light does not come on when then key is turned to the on position. I believe the light is working as it has flickered on a few times briefly over the last week since this charging system issue has occurred. There is voltage at the B+ and D+ terminals when the key is on. There is a W terminal but there isn't anything connected to it. I don't know if there had been a wire there before. I can't find any loose wires underneath the car.

Last edited by TheViolet; 09-21-2008 at 09:05 PM. Reason: left out a word
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post #2 of 3 (permalink) Old 09-23-2008, 06:23 PM Thread Starter
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The problem wasn't the wiring, the alternator itself, or even the regulator. It was the brushes. I had taken it apart and found that the brushes are worn....but not so much that they shouldn't be making contact. Apparently there was just enough dust from brush wear etc. that they weren't moving freely. Put it back together and started the car.....battery light comes on and system is charging no load @ 14.1 and loaded @ 13.87. Does anyone know if the brushes are replaceable or do I have to get a voltage regulator assembly? It couldn't tell if they are soldered....all the metal was fairly gray.


Last edited by TheViolet; 09-23-2008 at 06:24 PM. Reason: spelling.....
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post #3 of 3 (permalink) Old 09-23-2008, 08:10 PM
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I have found that any compenent electric motor repair shop can cut and grind brushes to fit your brush holders
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