Charging System: Description and Operation

The alternator supplies DC voltage to run the electrical system and to recharge its battery. The output of the alternator is controlled by a built-in voltage regulator.

When you first move the ignition switch to RUN, before the engine is started, voltage is applied to the charging system light through fuse 2. The indicator is grounded through terminal L of the alternator and the charging system light comes on.

With the engine running and the alternator working normally, voltage is still applied to the charging system light through fuse 2; but now, voltage is also applied from the alternator (terminal L). With equal voltage on both sides of the charging system light, the indicator light goes off.

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

The (ELD) electrical load detector measures the total electrical load on the charging system and provides a signal to the engine control module (ECM) which, in turn, controls the voltage regulator. When the electrical load is low, the field winding of the alternator is turned off to reduce mechanical load on the engine, and improve fuel economy.