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  #1  
Old 08-20-2012, 10:25 AM
300D-91's Avatar
Das German Diesel Mann
 
Join Date: Sep 2010
Location: Eastern PA
Posts: 285
Alternator Swap - OM602. 1991 300D 2.5 Diesel Turbo

After reading this thread on W123 alternator swaps combined with the fact that my 124 has always seemed to have low voltage I decided to look for a possible Mercedes replacement unit.

The one I selected (because it was given to me) came from a 1990 Mercedes-Benz 300TE 4matic and rated at 80 AMP vs. the 50 AMP unit in mine from the factory.

Before beginning the swap I had the donor unit tested at a local auto parts store and it passed! To be safe I elected to replace the regulator & brushes before installing it on the car.

The case was the same size and same bolt pattern as the old unit - in fact even the pulley was the same! One change did need to be made, the case needed to be rotated 90 degrees so that the connection point for the wires allowed proper routing of the wires.

The factory wiring for the 50 AMP alternator was very light gauge wire. In fact so light I decided to upgrade the alternator harness with a homemade harness comprised of dual 4 gauge wires. Another reason for a new harness was because the old unit used a connector that was incompatible with the new unit. The final reason is that since I haven't molested the original its easy to return to factory if it's ever needed.

I reused the heat shield to route my new harness then added split loom tubing to protect the new wires. And 6 hours later the job was complete.

There isn't much to see, but photos of the swap are on my Benz-Site.

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  #2  
Old 08-20-2012, 11:52 PM
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have also a 91 300D 2.5turbo which has an alternator made by Valeo. So far, no issues but
concerned brushes of volt. regulator worn. If you removed a Valeo wondering whether you
can give me the number on the voltage regulator. Tried to buy a new one but parts dealers
asking for a number. Thanks for your assistance.
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  #3  
Old 08-21-2012, 12:29 AM
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For others, here's some tips for upgrading the wiring - Installed a 143A alternator in my W124 (86-95E-class) - with photos

Sixto
87 300D
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  #4  
Old 08-21-2012, 01:42 AM
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Valeo alternators

Quote:
Originally Posted by diesel friend View Post
have also a 91 300D 2.5turbo which has an alternator made by Valeo. So far, no issues but
concerned brushes of volt. regulator worn. If you removed a Valeo wondering whether you
can give me the number on the voltage regulator. Tried to buy a new one but parts dealers
asking for a number. Thanks for your assistance.
I pulled a 120 Amp Valeo alternator out of a 2001 W210; the alternator is the same as the Bosch units seen in later 124s and early 210s. I don't know if the similarity goes back as far as your '91 as I have no experience with the 602 engine. I do know that the later alternators use different regulators and connectors than the early 124s but the date of the change is unknown to me.

The Valeo alternator is M-B part number 011 154 62 02; the regulator carries Valeo part number 2545472. I earched for a replacement regulator and found it almost impossible to find. I have been told that M-B dealers can get them but the price is ~$100, three times what I paid for the alternator!

A local alternator/starter rebuilding shop was able to sell me a pair of brushes for $10. They are not exact replacements but will fit and work and I can install them myself. You might try the same thing -- take the regulator out and have an auto electric shop in your area look it over. They may be able to cross it to an available replacement regulator, install new brushes, or sell you brushes to install yourself. Take the alternator too, in case they want to see it. Good luck, I think I'll avoid Valeo in the future.

Jeremy
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  #5  
Old 08-21-2012, 08:54 AM
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diesel friend: My old alternator was a Bosch. I'd be glad to supply the part # off the regulator when I get home, but it doesn't sound like that will help.

sixto: The harness that gsxr made looks very similar to the one I made. Great minds think alike!
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Old 08-21-2012, 11:39 AM
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Hmmm this is interesting as I was wondering what the 602 had on it for an alt..

I upgraded my M103 to a 143A unit a few years ago.

The 602 has a new alternator on it so I probably wont be installing anything to replace that for a while. But if I did it would be a 143a unit if it fits that is...
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  #7  
Old 08-21-2012, 01:40 PM
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JamesDean if I hadn't been given the 80 AMP unit the donor would have most likely been a larger capacity. At this point installing a different unit should be a snap since the new harness is fabricated and installed.
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  #8  
Old 08-21-2012, 05:55 PM
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Thumbs up

I put a 143A on my 603. Drop in fit, sans wiring obviously.
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  #9  
Old 08-21-2012, 08:49 PM
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I have been told by a very experienced auto elec that you can upgrade your bosch alt by simply replacing the reg with a reg that is for the higher amperage. The rotor excitation voltage is low enough so that even with the higher current it doesnt get near 12v. The core is the same dimensions & material so its unlikely magnetic saturation would be an issue.

Having pulled a few bosch alts to bits, I havent found any difference between the internals of a 60 amp & an 80 amp.
Has any one else tried this?
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  #10  
Old 08-21-2012, 09:06 PM
300D-91's Avatar
Das German Diesel Mann
 
Join Date: Sep 2010
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Quote:
Originally Posted by layback40 View Post
I have been told by a very experienced auto elec that you can upgrade your bosch alt by simply replacing the reg with a reg that is for the higher amperage. The rotor excitation voltage is low enough so that even with the higher current it doesnt get near 12v. The core is the same dimensions & material so its unlikely magnetic saturation would be an issue.

Having pulled a few bosch alts to bits, I havent found any difference between the internals of a 60 amp & an 80 amp.
Has any one else tried this?
I've wondered if a simple regulator upgrade would work. In fact I've found a web site that sells adjustable regulators and of course there is the old regulator mod using a diode.
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  #11  
Old 08-21-2012, 11:42 PM
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Alt. swap OM 602

Thanks for all the help. Was able to obtain a used 80 AMP Bosch out of a 190E,
2.6. and the brushes of the volt. reg. have quite a bit of life left.
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  #12  
Old 08-22-2012, 12:44 AM
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Late 124 diesel alternator swapping

Quote:
Originally Posted by layback40 View Post
I have been told by a very experienced auto elec that you can upgrade your bosch alt by simply replacing the reg with a reg that is for the higher amperage. The rotor excitation voltage is low enough so that even with the higher current it doesnt get near 12v. The core is the same dimensions & material so its unlikely magnetic saturation would be an issue.

Having pulled a few bosch alts to bits, I havent found any difference between the internals of a 60 amp & an 80 amp.
Has any one else tried this?
I replaced the 90A alternator in my '95 E300 with a 115A unit from a 1994 E420. The shapes were the same but the 115A alternator was definitely larger. The only required modifications were clocking the halves 180º and swapping the pulleys.

Incidentally, the regulators were not interchangeable -- physically different.

Jeremy



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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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