For 1990-2009 cars

The generator provides voltage to operate the vehicle's electrical system. The generator provides voltage to charge the battery. The regulator supplies current to the field coil of the rotor. A magnetic field is created when current flows through the field coil. The magnetic field rotates as the rotor is driven by the engine. This rotation creates an AC voltage and current in the stator windings. This AC voltage is converted to DC voltage by the rectifier bridge and is available to the vehicle's electrical system at terminal C1.

The generator must supply sufficient current to all vehicle electrical loads, especially for charging the vehicle's battery. Since the rotor speed varies with engine speed, the generator must also maintain the output voltage at a constant level. The regulator switches current to the field coil of the rotor on and off controlling the output voltage of the generator. When the ignition switch is in to the run position, battery voltage is supplied from the battery to the generator at terminal C1, turning on the regulator. The regulator switches on the field current by connecting the field coil of the rotor to the battery voltage available at terminal C1.

The field current creates a weak magnetic field in the field coil when the engine is being started. The regulator senses generator rotation by detecting an AC voltage at the stator through an internal wire. Once the engine is running, the regulator can monitor the internal AC voltage and DC output at terminal C1. The regulator varies the current in the field coil of the rotor as needed to provide a constant output voltage and adequate current to the vehicles electrical system.

Battery voltage is applied to the gauge cluster through fuse #15 whenever the ignition switch is in the ON or the START position. A ground is provided at the generator terminal C2 when the regulator senses a high or a low voltage condition or when the rotor stops turning. The charging indicator lamp illuminates if the battery voltage drops below 9.5 volts or exceeds 15 volts.