Charging System Description and Operation 7.2L / 7.8L

The generators feature the following major components:

The pulley and the fan cool the slip ring and the frame.

The generator features permanently lubricated bearings. Service should only include the tightening of mounting components. Otherwise, the generator is replaced as a complete unit.

The voltage regulator controls the field current of the rotor in order to limit system voltage. The regulator switches the current on and off at a rate of 400 cycles per second in order to perform the following functions:

At high speeds, the on-time may be 10 percent with the off-time at 90 percent. At low speeds, the on-time may be 90 percent and the off-time 10 percent.

The charge indicator illuminates in the IPC when the following occurs:

The generator provides voltage to operate the vehicle's electrical system and to charge its battery. A magnetic field is created when current flows through the rotor. This field rotates as the rotor is driven by the engine, creating an AC voltage in the stator windings. The AC voltage is converted to DC by the rectifier bridge and is supplied to the electrical system at the battery terminal.

The ECM monitors the state of the charge indicator control circuit. The ECM should detect a low circuit voltage when the Ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect a high circuit voltage.The ECM performs Ignition ON and RUN tests to determine the status of the charge indicator control circuit.The generator's voltage regulator controls current to the rotor, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. 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 the field current by controlling the pulse width. This regulates the generator output voltage for proper battery charging and electrical system operation. The generator F terminal is connected internally to the voltage regulator and externally to the ECM. When the voltage regulator detects a charging system problem, it grounds this circuit to signal the ECM that a problem exists. The ECM monitors the generator field duty cycle signal circuit to adjust the system voltage depending on electrical loads.The voltage regulator also uses a sense circuit, that is used by the regulator as the reference for system voltage control. On vehicles that use a sense circuit connected to the voltage regulator, this circuit must be operating properly for the charging system to work correctly, when there is a charging system concern all circuits at the generator should be tested before replacing any componets.Refer to system schematic to confirm if the vehicle being serviced uses the sense circuit as part of the charging system.

Charging System Description and Operation 6.6L / 8.1L

The generators feature the following major components:

The pulley and the fan cool the slip ring and the frame.

The generator features permanently lubricated bearings. Service should only include the tightening of mounting components. Otherwise, the generator is replaced as a complete unit.

The voltage regulator controls the field current of the rotor in order to limit system voltage. The regulator switches the current on and off at a rate of 400 cycles per second in order to perform the following functions:

At high speeds, the on-time may be 10 percent with the off-time at 90 percent. At low speeds, the on-time may be 90 percent and the off-time 10 percent.

The charge indicator illuminates in the IPC when the following occurs:

When the Ignition switch is placed in the RUN position B+ is supplied battery isolator control circuit. The battery isolator is used to isolate the auxiliary and primary batteries. When the Ignition is OFF only the auxiliary battery is being used so that the primary battery is not being discharged causing a no start condition. When the engine is running the generator(s) recharge all the batteries to maintain system voltage and keep the batteries charged.

The generator provides voltage to operate the vehicles electrical system and to charge its battery. A magnetic field is created when current flows through the rotor. This field rotates as the rotor is driven by the engine, creating an AC voltage in the stator windings. The AC voltage is converted to DC by the rectifier bridge and is supplied to the electrical system at the battery terminal.

When the engine is running, the generator turn-on signal is sent to the generator from the ECM, turning on the regulator. The generator voltage regulator controls current to the rotor, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. 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 the field current by controlling the pulse width. This regulates the generator output voltage for proper battery charging and electrical system operation. The generator F terminal is connected internally to the voltage regulator and externally to the ECM. When the voltage regulator detects a charging system problem, it grounds this circuit to signal the ECM that a problem exists. The ECM monitors the generator field duty cycle signal circuit, and adjusts the system voltage depending electrical load. On Vehicles that have a auxiliary generator the ECM uses the GEN 2 turn on signal to control the auxiliary generator, the auxiliary generator regulator does not use a F terminal. The two generators work together to maintain system voltage. The voltage regulator also uses a sense circuit, that is used by the regulator as the reference for system voltage control. On vehicles that use a sense circuit connected to the voltage regulator, this circuit must be operating properly for the charging system to work correctly, when there is a charging system concern all circuits at the generator should be tested before replacing any components. Refer to system schematic to confirm if the vehicle being serviced uses the sense circuit as part of the charging system