PeachParts Mercedes-Benz Forum - View Single Post - Electrical trouble; replace Alternator, Brushes or Voltage Regulator?

JimSmith · #4 01-26-2002, 10:38 AM

Ducati,

I agree with Dave and can tell you from personal experience that I have blown many a fuse without hurting the alternator, or the battery for that matter. I also do not see the connection between the event and the alternator. If you are having battery charging difficulties and they have just been noticed, you may have an alternator problem that is independent of the blown fuse.

There have been a number of recent threads here on the subject of voltage regulators, brushes and performance specs for alternators. Getting the alternator checked out correctly is more than just a voltage check, although if voltage is off the unit is clearly bad. Under no load conditions the voltage should be around 13.8 volts. At full load (lights, fans, etc. running but obviously not the glow plugs and starter) I cannot remember the value, but it is above 12 volts. If you meet both ends of the spectrum, you likely have an acceptable current output (amps).

The brushes are relatively easy to change, and can be found as separate items for a couple of dollars, or in a new voltage regularor assembly (easier, but costs closer to $40). The separate item repair requires some self motivation to take the old ones out, save some springs and manage to do some soldering, make a locking feature that keeps the brushes in the holder so the springs don't push them out, and so on. I have always opted for the new regulator.

If the alternator is not making the current rating, it likely needs to be rebuilt. I would opt for a rebuild from Fastlane or some other reputable supplier. Rebuilding an alternator is often viewed as no more than cleaning, repainting, pressing in new bearings, and installing a new voltage regulator. There is more to an honest rebuild, as it may need to be rewound, and likely needs a new rectifier section.

Hope this helps. Jim