Generator
The generator features the following major components:
• | The rotor with slip rings and brushes |
The pulley and the fan cool the slip ring and the frame.
The generator features permanently lubricated bearings. Service should only
include tightening of mount components. Otherwise, replace the generator as a complete
unit.
Regulator
The voltage regulator controls the rotor field current in order to limit the
system voltage. When the field current is on, the regulator switches the current on
and off at a rate of 400 cycles per second in order to perform the following functions:
• | Obtain the correct average current needed for proper system voltage control |
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.
Circuit Description
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.
When the engine is running, the generator turn-on signal is sent to the
generator from the engine control module (ECM)/powertrain control module (PCM), turning
on the regulator. 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 PCM. When the voltage regulator detects
a charging system problem, it grounds this circuit to signal the PCM that a problem
exists. The PCM monitors the generator field duty cycle signal circuit. The system
voltage sense circuit receives B+ voltage that is Hot At All Times through the ECM/TCM
fuse in the underhood junction block. This voltage is used by the regulator as the
reference for system voltage control.
This vehicle uses Class II and controller area network (CAN) communications.
The ECM/PCM are CAN and the body controller systems are Class II. The body control
module (BCM) acts as the gateway between the different communication protocols. The
ECM/PCM requests the battery lamp on the CAN communication line and then the BCM sends
a request to the IPC for lamp illumination.
The ECM/PCM will request the battery lamp on under the following conditions:
• | The ECM/PCM interprets the ignition is in the accessory position. |
• | The ECM/PCM is in the RUN power mode with the engine not running. |
• | Generator L terminal fault has been detected. |
• | Generator F terminal fault has been detected. |
If the generator is not charging, it pulls the F terminal low causing an F terminal
fault. Low voltage threshold is 10.5 volts for 4 minutes and engine
at least 1,300 RPM. High threshold is 18 volts for 5 minutes.