Circuit Operation - Charging System

The basic charging system consists of a generator with an internal voltage regulator. The generator supplies DC voltage to operate the 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 the 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 Pulse Width Modulated (PWM) 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 the engine is running, the regulator varies tile field current by controlling the pulse width, regulating the generator output voltage. The regulator controls the 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 the 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 the Generator.

L Terminal And Volts Indicator
The L (lamp) terminal is connected internally to the voltage regulator and externally connected to the IPC. The L terminal is used to enable generator operation. The IPC sends out 12 volts on CKT 225 through an internal 510 ohm resistor to allow the generator to turn ON. (If tile wire to the L terminal is open or grounded, the generator will not turn on.)

The regulator internally grounds terminal L when it detects one of the following: an open or short in CKT 225, an under- or over-voltage condition, a broken drive belt, an open or shorted field circuit, or malfunctioning regulator. The IPC senses this ground and displays tile BATTERY NO CHARGE message on the Driver Information Center (DIC). The IPC and PCM also monitor system voltage and set codes for under- or over- voltage conditions. For export vehicles, a telltale also lights on the IPC.