BMW E28 alternator not charging
Why is my E28 alternator not charging?
The most common cause is a faulty voltage regulator, meaning the carbon brushes at the back of the alternator. On a Bosch alternator the regulator comes off with two screws without removing the alternator. The connector going to the alternator regulator may also be corroded.
Why does charging only work at high revs?
The cause can be a corroded alternator wire connector on the side of the engine. Replacing the regulator may only help for a short while. Also check the belt tension, because a loose belt does not spin the alternator properly.
The charge light stays on all the time or the battery drains – what causes it?
The cause can be a slight short circuit between the alternator's positive and negative wires, or a worn groove in the alternator's copper ring. Disconnect the wire that runs from the battery to the alternator via the starter: if the light still stays on, the fault is somewhere other than the alternator.
Where do the alternator grounds connect?
The alternator is grounded to a bolt behind the alternator that is attached to the body, and a second ground goes to the engine block. Also check the ground cable between the engine and the body for losses.