Starting and Charging: Description and Operation
CHARGINGThe 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. (On the 4.6L powertrain with this option, the generator has three leads wired in this way, but no accessible output terminals.)
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.
STARTER
When the ignition switch is moved to the START position and the gear selector lever is in PARK or NEUTRAL, battery voltage is supplied to the normally-open contacts of the starter enable relay. Voltage is also supplied through tile park/neutral position switch to the starter enable relay coil. At the same time, a start request is sent to tile PASS-Key � II decoder module. If correct PASS-Key(R) II system resistance is sensed, then the PASS-Key(R) II decoder module energizes the starter enable relay by grounding on one side of the relay coil. (The PASS-Key(R) II decoder module also provides the PCM cranking fuel enable signal.)
Once the starter enable relay is energized, the normally-open contacts close, completing the circuit to the starter solenoid. When the starter solenoid circuit is completed, both the hold-in and pull-in windings are energized. The circuit through the pull-in winding is completed to ground through the starter motor. The windings work together magnetically to pull and hold in the plunger. The plunger moves the shift lever. This action causes the starter drive assembly to rotate as it engages with the flywheel ring gear on the engine. Rotating at the same time, the plunger also closes the solenoid switch contacts in the starter solenoid. Full battery voltage is applied directly to the starter motor and it cranks the engine.
As soon as the solenoid switch contacts close, current stops flowing through the pull-in winding because battery voltage is applied to both ends of the windings. The hold-in winding remains energized; its magnetic field is strong enough to hold the plunger, shift lever, and starter drive assembly solenoid switch contacts in place to continue cranking the engine.
When the ignition switch is released from the START position, battery voltage is removed from the PPL wire and the junction of the two windings. Current flows from the motor contacts through both windings to ground at the end of the hold-in winding. However, the direction of the current flow through the pull-in winding is now opposite the direction of current flow when the winding was first energized.
The magnetic fields of the pull-in and hold-in windings now oppose one another. This action of the windings, along with the help of the return spring, causes the Starter drive assembly to disengage and the solenoid switch contacts to open simultaneously. As soon as the contacts open, the starter circuit is turned off.