Your problem is caused, as others have said, by a short circuit in the alternator or the regulator. The regulator should be part of the alternator; it bolts in at the back (2 screws) and can be removed with the alternator still in the car. Use the search function for "regulator" and you should bring up lots of threads and photos. It's easy to R&R.

If the regulator checks out OK (test by replacing with a known good one) then the problem is a shorted diode in the alternator itself, requiring replacement of the whole alternator -- no separate diode board, unfortunately, as in BMW motorcycles.

__________________

"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