I recently had a slew of charging problems in my '79 240D. After replacing the voltage regulator (which you took care of with new alternator) I put the battery on a charger overnight, and make sure the belts are tight and not worn out. A slightly loose belt was causing me lots of headaches, I believe. Tighten that alternator up real good, and put some of that belt dressing junk on the belt if you don't have a new one handy. Working for me, so far. *knock on wood*