I recently replaced the starter in my 1988 760 after having to tap it with a hammer to get it going one day which seemed like a logical indication that it was bad, even though the electical connections were covered with grease and oil, which I found out later.
I was then informed that the alternator was actually preventing the car from running as it quit completetly on the way home,even though the brand new battery had plenty of voltage.
Now I'm wondering if the starter was actually worn out or was the alternator the problem to begin with?
How can I be sure this the problem has been accurately diagnosed
this time?
Or is it time to get a different mechanic?

Thanks for you help.
Peter