BMW E32 alternator not charging and charging light does not come on
Why does the E32 charging light not come on and the alternator not charge?
The alternator gets its excitation current from the ignition switch through the charging light. If the light does not come on, the alternator does not excite. The cause is often a broken or poorly connected exciter wire at the back of the alternator, an oxidised voltage regulator earth or a faulty bulb. The light should come on with the ignition on and go out once the engine has started.
How do you find the cause of a charging fault?
Measure the voltage with the engine running: normal charging is about 14 V. With the ignition on, connect the exciter wire to ground, and the charging light should come on. Also check the alternator power cable, the connections and the engine earth before removing the alternator.
When do the voltage regulator or brushes need replacing?
Worn brushes weaken charging and can make the charging light flicker at low revs. Sometimes the warning lights in the instrument cluster come on and the electrical equipment shuts off while driving. The regulator and brushes can be replaced without removing the alternator. If the bearings are worn, the alternator or the bearing must be renewed.