My son inadvertantly installed a new battery in our project - 1982 BMW
528e - backwards. In this reversed polarity situation, he tried several times to start the car. When I got home from work, I discovered the error, removed and reinstalled the battery. Much to my surprise, the car started and ran until I turned the ignition off. Unfortunately, the battery charging light came on (probably was on before I started the car and I didn't notice...). I pulled all the fuses one by one; no change. I disconnected the negative, disconnected the alternator, reconnected the battery and no light. So the question is: rebuilt alternator or change the diodes (how hard is this?)? Thanks, Mark