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03-08-2005, 08:16 AM
I just started having problems with my charging system on my 81 300D. At idle speeds the battery light is lit. I checked the voltage at the battery and it is a steady 13 volts. Once I'm at highway speeds the battery light goes out. After driving for at least 30 minutes I can have the car idle without the battery light showing. I've had alternator problems on other cars (Domestic), but once the alternator is dead there is no charging. It seems there is charging taking place, but only at higher rpm's. Is there an adjustment on the voltage regulator?
Any help would be appreciated.....Thank-You in advance...Joseph...

03-08-2005, 11:21 AM
the voltage regulator on the back of the alternator also holds the
brushes - which wear out in 75-100,000 miles depending on how much dirt enters the motor room . Simple and cheep to replace - cause of 80% of charging failures on this car. Just remove NEG. BATT. cable, unplug regulator, unscrew 2 small holding screws, rotate the regulator out - rotate the the new long brushes/regulator back in place , tighten two screws, connect battery = "Bob's yer Uncle " !

Creighton Demarest

03-09-2005, 01:06 AM
Your information was right on the money. The repairs were completed in less than 1/2 hour. Thank-You again....Joseph...

03-09-2005, 11:56 AM
... it was very common and easy , glad I could help.

keep in touch, enjoy the greatest Diesels made.

Creighton Demarest
Darien, CT.

my german fleet:

02-13-2006, 05:24 PM
I have a 85 300 D with 280,000 miles. Same problem and changed the voltage regulator. Worked like a champ. 30 days later I am back to the exact same problem. Could the voltage regulator have gone bad that quick or is there something else?


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