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 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 system voltage sense
circuit receives battery positive voltage that is Hot At All Times through
the ALT Sense 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 instrument panel cluster (IPC) illuminates the charge indicator when the
following occurs:
| • | The powertrain control module (PCM) detects that the generator
output is less than 11 volts or greater than 16 volts. The IPC receives
a discrete input from the PCM requesting illumination. |
| • | The IPC performs the displays test at the start of each ignition cycle.
The IPC illuminates the charge indicator. |
| • | The ignition is on, with the engine off. |
