Circuit Operation - Charging System

The basic charging system consists of a generator with an internal voltage regulator. The generator supplies DC voltage to operate tile vehicle's electrical system and to charge the battery.

The regulator provides current to the generator's rotor. Current flowing through the rotor creates a magnetic field. The field rotates as the engine drives the rotor, creating an AC voltage in three stator windings in the generator. AC voltage is changed to DC voltage by the rectifier bridge. This DC output is applied to the battery and the vehicle circuits at tile BAT terminal of the generator.

The PCM (4.6L) or IPC (4.9L) initiates generator operation by supplying 12 volts, through an internal resistor, to the generator L terminal over CKT 225. The generator regulator applies voltage to the rotor as a PWM (pulse width modulated) signal to energize the field windings.

When the engine is started, the regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once tile engine is running, the regulator varies tile field current by controlling the pulse width, regulating the generator output voltage. The regulator controls tile charging system voltage and therefore tile ampere rate of battery charge and power supplied to the vehicle.

The generator S terminal is used with the powertrain for remote voltage sensing to more accurately control tile charging voltage.

Vehicles with tile heated windshield option (C50) are equipped with a generator that has three insulated terminals next to the OUTPUT terminal to make three-phase AC power directly available to the heated windshield power module. On vehicles equipped with this option, the stator is connected directly to the three output terminals on the back of tile Generator. (On the powertrain with this option, tile generator has three leads wired in this way, but no accessible output terminals.)

L Terminal And Volts Indicator
The L terminal is connected directly to tile voltage regulator and externally to the PCM. The L terminal is used to enable generator operation only after the engine is running. Through an internal resistor, the PCM sends out 12 volts on CKT 225 to allow the generator to turn ON.

Once the generator is turned ON, the regulator receives its supply voltage from the output stud and the generator is then self-energizing. The PCM can turn off tile generator by turning OFF tile 12 volt signal to tile L terminal using PCM override PS23.

This terminal is also used by the generator to indicate internal faults. The regulator grounds tile L terminal when it detects an internal problem. A fault changes the value of CKT 225 in tile PCM to low. The IPC detects tile ground via the UART data line message from the PCM and displays tile BATTERY NO CHARGE message on tile IPC (USA clusters). In this case, a P110 code sets. For export vehicles, The VOLTS telltale lights on tile IPC.