Description & Operation

WARNING: Vehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see AIR BAG DEACTIVATION PROCEDURES in AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS.

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

The Denso generator is electrically similar to earlier models. The generator features the following major components: The delta stator, rectifier bridge, rotor with slip rings and brushes, a conventional pulley, dual internal fans, and regulator. The pulley and fan cool the slip ring and frame. The generator features permanently lubricated bearings. Service should only include tightening of mount components. Otherwise, replace generator as a complete unit.

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 control radio noise control, and to 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.

The generator provides voltage to operate the vehicle's electrical system and to charge it's 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 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 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 battery positive voltage that is Hot At All Times through the DIM fuse in the rear fuse block. This voltage is used by the regulator as the reference for system voltage control.

On Limousine models, a primary and secondary/auxiliary generator is equipped. The primary generator is the standard equipment generator. The secondary generator is a smaller generator. This generator is used to maintain battery voltage over an extended idle period with high loads and functions the same as other generators, but is not PCM controlled. When engine is running, power is sent to the battery positive voltage sense circuit, turning on the regulator. The regulator uses the input voltage to control the output of the generator. The battery positive voltage output circuit of this generator is connected to the battery positive voltage terminal on the underhood bussed electrical center. The wiring harness for this generator also contains a test terminal for the lamp circuit of the generator.

The Instrument Panel Controller (IPC) illuminates the charge indicator when the following occurs:

PCM detects that generator output is less than 11 volts or greater than 16 volts. The IPC receives a Class 2 message from the PCM requesting illumination.
IPC determines that system voltage is less than 11 volts or greater than 16 volts. The IPC receives a Class 2 message from the Dash Integration Module (DIM) indicating system voltage.
IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

The IPC will also illuminate the following indicators in the Driver Information Center (DIC) when a generator malfunction is present:

BATTERY VOLTAGE LOW-6 - The IPC illuminates this indicator in the DIC when the IPC determines that system voltage is less than 11 volts.
BATTERY NOT CHARGING-7 - The IPC illuminates this indicator in the DIC when PCM detects a malfunction with the generator output. The IPC receives a class 2 message from PCM requesting illumination.
BATTERY VOLTAGE HIGH-8 - The IPC illuminates this indicator in the DIC when the IPC determines that system voltage is greater than 16 volts.
SERVICE CHARGING SYSTEM-102 - The IPC illuminates this indicator in the DIC when the PCM detects a malfunction with the generator output. The IPC receives a class 2 message from PCM requesting illumination.