It looks as if my alternator is marginally charging the batter during operation. I can see the batter light on the dash very dimly glow when at a stop-sign, and it is running down into a no-start situation here and there. I actually think that there is an electrical leak also, but my first object or line of attack is the alt.

Somewhere in these forums I think I had read that it is possible to just replace your alternator brushes to restore good amperage, and that this operation can be done without removing the alt from the car. Does this sound correct to anybobe? Can I get a confirm that this is worth trying?

It seems logical because brushes could seem to wear out and start loosing contact after 200K miles or so....

If this is not worth trying, how tough is it to pull and replace an alt for a moderate level home-mechanic?

This link has the pictorial for replacing the alternator brushes / voltage regulator.

http://www.dieselgiant.com/mercedesvoltageregulatorinstall.htm

They same symptom could also be a loose Fan Belt.

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84 300D, 82 Volvo 244Gl Diesel

That's exactly what I needed, thanks very much. The pictures make it crystal clear!

Do you think most auto-parts stores would have that bosch part, or am I going to need a benz specialist?

Mercedes Parts are numbered with a separate MB number in addition to the
Manufacturer's (In this case Bosch).
If you know the Year and Model Number of your MB you can look up Parts #s
here:

http://www.detali.ru/cat/oem_mb0.asp?TP=1

or Click on "Buy Parts" at the top of page and follow prompts.

Do (if you find you need one) acquire a Genuine Bosch regulator,at the least,
if not a Genuine Mercedes Regulator.

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'84 300SD sold
124.128

So just now I did some fiddling with my DVOM meter and found that with the negative cable to battery disconnected (no key in ignition), and running the meter between the neg-cable and neg battery-terminal, the best and most stable reading I could make was about 1.45milli-amps. Would this be a normal reading, or should it be zero? Would the 1.45mA be the dash-clock maybe?

Another possibility might be that the alt is shorted out, and that's the mA drain I'm reading? I've heard that alts can short out once they get older. Just thinking out lout here...

I'm still certainly going to need to address the low alternator-juice situation (not charging strongly), but I also would like to make sure that I'm not dealing with draw-down leakages while it's parked.

Thanks all for your interest....

that low of current draw is prolly acceptable- the clock, radio, and a few other vampires are always drawing juice.

I've had bad alts do that, they usually draw 7-8 amps in my experience.

I have pulle d afew sets of brushes out of Bosch alt's at the junkyards, so I carry a spare used one in my car. otherwise an auto- electric shop can help you out( rebuilds alts and starters, etc)

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

yep get the bosch from fastlane. my NAPA one lasted 6 months. second NAPA one did not work at all.......

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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

So that's a good pictorial on the voltage regulator. But what about the original question about brushes? Are there brushes in the alternator that can wear out as well?

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

brushes are part of the VR... at leats on 123

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

Oh.......thanks

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

OK. So today I had time after getting off work to check the belt running to the alternator and I must say I think it seems loose. If I pull on it, it deflects maybe an inch, and doesn't feel taught, and if I push on it between the wheels in one spot, it will push in at least four to five inches and feels even looser.

What should I expect with the feel of this belt when new or almost new? I guess I should have checked this in the first place, but I learn as I go....

It looks like it might be rather difficult to replace that belt as it's the deepest one in the network. Is this one better left to a shop? Also, it looks like there might be a way to adjust the angle and thus the tension by moving the angle of the alt out away from the engine body (via a bolt at the top looking down). Is that what the bolt and channel is there for?

Thanks as always.

That's quite loose. The service manual uses a special tool to measure the tension of the belts, the Haynes manual says 1/4" to 1/2" deflection, depending on the distance between the pulleys.

Changing belts is not difficult, just a pain. Put the car up on ramps and it'll be much easier. Each component has 3 bolts to loosen then you loosen/tighten the adjuster bolt (the bolt and channel like you said) which rotates the component either toward or away from the crank pulley, which adjusts the belt tension.
It wouldn't be tough to just tighten the alternator belts. Replacing them takes more time...since they're the deepest, like you said.

PM me your email, I can send you the pages from the service manual, they're too big to post here.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now