Hello, the alt. failed on my 1993 M-B 300D, had a new rebuilt installed, it would not charge.
Installed 2nd Alt. it would not charge. Took Alt. to rebuilder who ran it on the test bench, it charged as per specs. Reinstalled on vehicle, will not charge. Has voltage to alt. from batt. also has a good ground. Help , before I slash my wrists in agony.
Regards, Lgriffi

 

Have checked the fuses on the overvoltage relay, they check OK. This thing has me pulling my hair out. Lgriffi

 

Have you replaced the voltage regulator? The VR regulates the voltage for the electrical system including trickle charge the battery after engine start. Assuming the springs and brushes in the alternator are not worn, the other component in the electrical system (other than the battery)is the VR. Note the battery is only used to provide power (apprx 20 amps) to the starter. I hope this helps.