500 miles without electricity and how to fix it! (alternator rebuild)
 

Hello to all,

I purchased an Ebay 1984 300D turbo and during the drive from California
to Arkansas I begin to lose several functions. First the radio and AC
then the window were very slow rolling down. My battery was a 1000 amp
unit but my alternator failed. I never shut the car off and did my refueling
with the car running. :D

Made it home safe and sound. I am now hooked on the old diesel Mercedes.
Battery voltage was 5.75 VDC! Luckly I made it before it got dark!

Now the fix.

After a little rest I put the battery on charge until 12.8 volts was reached.
The car started right up and my digital fluke showed a stable reading of
12.5 VDC. No charging was taking place. I revvvvved the motor up
and the alternator would charge some times and some times it wouldn't


Disconnected negative battery lead!!!!!!!!!!!!!!!!

I removed the alternator and it looked new. I found a tag which
said " rebuilt, made in Germany.

I removed the regulator/ brush assembly. The armature rings (2) were
black but not in bad shape. The brushes were very worn. Length 1/8".

I went to a local motor rebuild shop with part in hand. They did not
have my exact regulator but they gladly installed two new brushes and
soldered the wires in place. They provided a small piece of sand paper
to clean up my armature rings.

I cleaned the armature rings and installed the regulator/brushes (easy)
tightened the two screws and reinstalled the alternator. 17MM wrench.

Results: I have a Fluke DC amp clamp and Fluke digital volt meter.

With both meters in place I fired the car up and here are my readings.

12.9V @ 26 amps! (battery was in need of some charging)

I drove the car on some back roads for about 20 minutes and then
re-tested.

13.5V @ 16 amps!

Tested again the next day after driving to work.

14.2V @ 6 amps!

Total cost $19.95 and about 2 hours of labor. :)

I hope this helps someone else.