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 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.
Charging System Indicator
The IPC illuminates the charge indicator in the message center when the following occurs:
| • | The PCM detects that the generator output is less than 11 volts or greater than 16 volts. The IPC receives a class 2 message from the PCM requesting illumination. |
| • | The IPC determines that the system voltage is less than 11 volts or greater than 16 volts. The IPC receives a class 2 message from the body control module (BCM) indicating the system voltage. |
| • | The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds. |
| • | The ignition is ON, with the engine OFF. |
