[Lynn]

Dan:

Between my brother and I, we have owned over 40 bimmers. Currently have 7 in the family. Check to see that your alt belt is not glazed or just a bit loose. On an 85 model, there are rubber bushings in the alt mounting holes. They get real spongy over time and the alt gets just a bit cocked, making it more likely to slip the belt just a bit. With the engine off, if you can "spin" the alt pulley with your hand using just the leverage you can muster with the alt fan, then the belt is probably slipping and not charging the battery sufficiently. Tightening the belt will only be a temp fix. You will need to get new mounting hole bushings. Easy to replace.

If the alt tested fine then the regulator is probably OK. It is integral, with the brushes built in, and, believe it or not, can be replaced easily without even removing the alternator. Take out the two mounting screws and the assembly comes out with the brushes attached. New one comes with new brushes. However, NORMALLY, if the brushes are worn out the red light on the dash starts coming on intermittently. The regulator itself is electronic and RARELY goes bad. I have never seen a bad one.

Hope this helps.

Lynn