For 1990-2009 cars

### Generator

The generator features the following major components:

• | The delta stator

• | The rectifier bridge

• | The rotor with slip rings and brushes

• | A solid pulley

• | Dual internal fans

• | The regulator

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:

• | Radio noise control

• | 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), 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 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.

### Charging System Indicator

The instrument panel cluster (IPC) illuminates the charge indicator in the message center when the following occurs:

• | The ECM detects that the generator output is less than 11 volts or greater than 16 volts. The IPC receives a serial data message from the ECM requesting illumination.

• | The IPC determines that the system voltage is less than 11 volts or greater than 16 volts. The IPC receives a serial data 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.