Bat Drain
The new regulator will take care of the main drain.
Unfortunately, E9s charging system is a crossover. That means the diodes are inside the end of the Alternator if original type. Check yours and see. One of the many diodes ( excitor) is causing the red light to stay on. You can have it repaired ( New diodes are still available from BMW) or a rebuilt from Autozone shows up as about $45. Napa was higher.
The new regulator will take care of the main drain.
Unfortunately, E9s charging system is a crossover. That means the diodes are inside the end of the Alternator if original type. Check yours and see. One of the many diodes ( excitor) is causing the red light to stay on. You can have it repaired ( New diodes are still available from BMW) or a rebuilt from Autozone shows up as about $45. Napa was higher.