143 amp alt in 300d 2.5
 

Thanks to information i received here i was able to get and install a 143amp alternator on my 91 300d 2.5. now even with my headlights on and the a/c on high at idle it never goes below 13.6 measured at the cigar lighter which seems to be about .2 below the batt voltage with different meters.before the change, in city traffic it would get down to 11.5 or so with only the a/c on.
The old alternator was a 70amp made by Iskra in Slovenia and was not getting the job done and was putting out a bit over 2ac volts,and causing most of the warning lights along the bottom of the instrument panel to be lit at times.The new alternator shows only .095mv ac and all lights are out with the engine running. Don:D

Great fix!

I wonder why MB put these undersized alternators in the diesel cars...

I just replaced mine with a 135Amp from a Saab. Now even with the defogger, headlights, windshield wipers, rear defogger, and radio on, everything works as it should. Before I had to kill the radio and switch between front and rear defogger or the "ALT" light would come on...
And that was with a new voltage regulator!

With AC noise that large, it sounds like a some of the diodes were going and making the problem worse than it otherwise might have been. A better alternator, fix of intermittant electrical wierdness and and upgrade all in one chore.. doesn't get much better than that :D