When the original Bosch alternator failed on my '84 TD several years ago, I installed an upgrade used Bosch 90A unit - mainly because a friend gave the replacement to me.
I left the original B+ twin-plug harness disconnected but secured with a bracket and sleeve I made from some rubber hose, and fastened to the 90A unit. Then I piggybacked a battery cable to the 8mm B+ stud on the starter, connecting the other end to the 6mm B+ alternator stud.
I used one of those European-style battery cables that has the stamped battery terminal with a 6mm bolt. Then I removed the 6mm bolt and cut off part of the battery terminal, leaving one 6mm lug on the cable to connect to the 6mm alternator stud.
I realize my W123 engine setup is different than yours, but hopefully you'll be able to fit something similar.

Happy Motoring, Mark

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DrDKW

I'll probably just end up modifying the harness. I'm posted a new thread here:

Alternator upgrade wiring questions (with photos!)

It has photos of the carnage and a few questions.

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RenaissanceMan Labs: where the future is being made today.

Garage:

2017 Chevy Colorado Diesel (nanny state emissions)
2005 Volvo S40 T5 AWD, 77k
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 113k - 28.6 mpg

WARNING: this post may contain dangerous free thinking.

Reading this thread scared the sh** out me.

I checked all of my pulleys and they are ok
However the water pump and alternator pulley have the slightest bit of drag and roughness to them. Going to change them before they get really bad.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

http://www.w124performance.com/images/W124_stereo/white_87/


http://www.peachparts.com/shopforum/performance-paddock/53237-installed-143a-alternator-my-w124-86-95-e-class-photos-2.html

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'84 300SD sold
124.128

The "Special Pulley" relieves the TENSIONER system of excess load caused by
the Heavier Alt's spinning mass and inertia.
(It will also SAVE your Harmonic Balancer from the same fate.)

I believe (as Dave says) it's not really needed until you go up to 120 Amps.

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'84 300SD sold
124.128

This morning I got the alternator installed, minus the wiring. Now I can at least move the car around my garage if I need to. The clutched pulley is 56mm and the stock pulley is 50 mm. Despite requiring about 10mm of extra belt as compared to stock, it worked with a stock belt no problem and the tension seems perfect, with about 1/2 inch of deflection when gently pushing on the top span of the belt.

It's smooth as silk and much quieter. I'm a happy customer. I don't really want to run new wiring, so I'll probably just hack the stock harness. I'll never put the old-school style alternator back in there now that I have a modern one.

I highly recommend the clutched pulley upgrade, even with the stock 70A or near-stock 90A unit. There is a reason that all modern cars use clutched pulleys. I have heard a 1-2% bump in fuel efficiently is to be expected with that upgrade.

__________________
RenaissanceMan Labs: where the future is being made today.

Garage:

2017 Chevy Colorado Diesel (nanny state emissions)
2005 Volvo S40 T5 AWD, 77k
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 113k - 28.6 mpg

WARNING: this post may contain dangerous free thinking.

I cannot help but notice that your alternator problem happened on 4/19 and you posted that it was a mechanical failure. How come it morphed to be an electrical problem? It does not make sense as alternator R&R is straight forward. You need to go back to square one and see what you have or have not done.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.