IMO, I would NOT buy that alternator from those people. The only picture we see is the housing and nothing else. It probably would need to have a load of cash put into it to rebuild.

Keep in mind that any "high output" model is a compromise. Even the 115Amp bosch is a compromise. Your alternator should say on it the amperage rating. if it is 80-80amp I would think that would suffice for that body style however if you need an upgrade, I am sure someone here will know what fits

What does it take to rebuild an alternator ? I think the only part that would be worn the fastest would be the brushes. My IP leaks fuel for a few months and oil seems to have leaked a bit inside. But I put new regulator (new brushes althought the old one didn't wear out at all) in there and took it to Kragen yesterday to test it, the test passed. Does it mean anything ? Thanks . I suspect some leakage current somewhere, a short somewhere maybe in the car. It doesn't charge enough, it seems.

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1992 300SD, 290K miles.

Usually the only wear items are the brushes (part of the VR ass'y) and the bearings. A rebuild normaly consists of replacing both, cleaning & painting the housing, and slapping a 'rebuilt' label on the outside. If you have a 1992 car you have a serpentine belt alternator, and there are plenty of used ones available cheap... you can upgrade to a 143A or 150A unit for a little over $100. What makes you think it "doesn't charge enough"? You may have a current drain somewhere in the car, the alternator may be fine...

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Could you give me the part number for the 143A or the 150A ?

http://cgi.ebay.com/ebaymotors/ALTERNATOR-MERCEDES-600-S-CLASS-92-93-94-95-58486_W0QQcmdZViewItemQQcategoryZ33573QQitemZ7993425937
What about this one ?

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1992 300SD, 290K miles.

Where does the field wire goto? +battery?

Pretty sure that eBay link is for a 110-120A unit. You need something from 1996-up, per this document:
http://www.w124performance.com/docs/mb/other/alternators.pdf

The battery (B+) terminal goes to the battery positive terminal. The smaller post (D) connects to the small wire. Here's the replacement harness I made when I upraded from 70A to 150A:

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Goes to the light on the dash oddly enough...its a sorta long explanation but trust me

Also rebuilts are just make things shiney, replacing bearings, inpect rotor and stator and put in a new regulator/brush setup.
Usually the diodes are fine (test those too). I very rarely ever had diodes burn up in most alternators...the alternators off of mid 90's jeeps like to smoke rectifiers

To replace bearings you almost always need a press to get the bearings off/out shafts/of housings. If you try a hammer and heat it just doesn't work. The press makes super easy work of it. The cases are not as strong as they might seem

That cable supported on the engine side of things? I can imagine a diesel engine vibration could wreak havoc on the post on the alternator if not

Nice harness though...

ROTFL!! The OM603 engine doesn't vibrate, my OM617 friend! Seriously though, I'm not worried about vibration issues. It's all nice and solid. A bunch more photos are here:

http://www.w124performance.com/images/W124_stereo/alternator/

Note that I originally had a 143A then bumped up to a 150A.

What kind of Voltage is that thing putting out at idle (with and/or without load)?

My car has a W140 body with the 3.5L 603.917 engine. If I were to opt for a 143A or and 150A, which of those listed in that PDF file should I go for ? Thanks.

Edit: I've just read the footnote in that PDF files and it looks like it should fit physically. But on the older cars, one must reuse the pulley. Is this correct ? Thanks

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1992 300SD, 290K miles.

Full details are in this thread:

Installed a 143A alternator in my W124 (86-95E-class) - with photos

Basically, it puts out over 14V at idle with up to 100A load (yes, still at idle!) with a warm/hot alternator. The 150A is even better. The voltage is higher when cold. This isn't really necessary unless you have extra electrical loads... I have megawatt headlight bulbs, and a serious stereo system too... would like to add heated seats some day as well.

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Tough call. I buy used parts from salvage yards, and as long as I can get a 143A or 150A from the right year/model, I'm not picky. You may need to re-clock it to get the posts away from other things like oil drain pipes. If you wanted a specific Mercedes part number to order, try the part number on the 150A unit in my photos at the link above. The cost is pretty steep though... rebuilt is $300-$400 I think, or new will be $600-$900...!

It's a simple bolt-in on the W140 diesel, although you are correct that you must swap your original diesel pulley onto the bigger alternator (or buy a new pulley for it if you can't get the old one off.) Physically there is no problem with fitment.

I've just heard that someone in Oakland California can rebuild the Alternator and change the diodes and maybe increase the winding to increase output capacity. I wonder if that's true. From what I read on this thread, the higher capacity Alternator is heavier, does that mean it's also a bit bigger physically ?

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1992 300SD, 290K miles.

Noooooo no no no no, you do NOT want to have your original alternator rewound for more output. This will give you more peak output but you lose idle output! Rewinding is only a decent option if you can not get a larger OE alternator to bolt up, or need more peak output from a physically smaller unit. That doesn't apply to any Mercedes made after about 1980 or so, we can get larger Bosch units for our cars.

The Bosch 143A and 150A units are larger than the little 70/80A units, and they also put out more power at idle speed than the small units can deliver at peak output. They still fit OK. There are some photos of both side by side on y website (link above), you can see the difference.

Trust me... the easy route here is to get a used 143A or 150A unit (preferably a low-miles one) if you need more output. For your specific case though, I think you have a power drain somewhere, since your stock alternator tested OK.