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 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 A/C voltage
in the stator windings. The A/C 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
generators 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 A/C 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 system voltage sense circuit receives battery positive voltage
that is Hot At All Times through the PCM/ECT fuse in the under-hood junction block.
This voltage is used by the regulator as the reference for system voltage control.
Charging System Indicator
The driver information center (DIC) illuminates the charging system failure
driver warning when the following occurs:
| • | The body control module (BCM) sends the serial data message indicating
that the generator output is less than 11 volts or greater than 16 volts. |
| • | The DIC receives a serial data message indicating a charging system/generator
fault from the PCM. |
