Charging System: Description and Operation

The alternator supplies DC voltage to operate the car's electrical systems and to recharge its battery. The output of the alternator is controlled by the built- in voltage regulator.

When you turn the ignition switch to RUN, before the engine is started, voltage is applied to the charging system light through fuse 24. The indicator is grounded through terminal L of the alternator, and the charge indicator light goes on.

With the engine running and the alternator operating normally, voltage is still applied to the charging system light through fuse 24; but now voltage is also applied from the alternator (terminal L). With equal voltage on both sides of the charging system light, the indicator does not go on.

When the engine is running and the alternator is not charging, the charge indicator light is grounded through the alternator (terminal L). The charging system light goes on to alert the driver that the alternator is not charging properly.