Generator
The AD-237 generator is electrically similar to earlier models. The generator features the following major components:
| • | The delta stator |
| • | The rectifier bridge |
| • | The rotor with slip rings and brushes |
| • | A conventional pulley |
| • | Dual internal fans |
| • | The regulator |
The pulley and the fan cool the slip ring and the frame.
The AD stands for Air-cooled Dual internal fan; the 2 is an electrical design designator; the 37 denotes the outside diameter of the stator laminations in millimeters, over 100 millimeters. The generator is rated at 125 amperes.
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 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. 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.
When the ignition switch is turned to RUN, the charge indicator turns on for a few seconds (bulb check), then turns off. The powertrain control module (PCM) commands the bulb of the charge indicator on by sending a Class 2 serial data line message to the instrument panel cluster when the PCM detects a charging system problem.
Charging System Indicators
Charge
The IPC illuminates the charge indicator 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 performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds. |
BATTERY NOT CHARGING - 7
The IPC illuminates the BATTERY NOT CHARGING - 7 indicator in the DIC when the PCM detects a malfunction with the generator output. The IPC receives a class 2 message from the PCM requesting illumination.
BATTERY VOLTAGE HIGH - 8
The IPC illuminates the BATTERY VOLTAGE HIGH - 8 indicator in the DIC when the IPC determines that the system voltage is greater than 16 volts.
BATTERY VOLTAGE LOW - 6
The IPC illuminates the BATTERY VOLTAGE LOW - 6 indicator in the DIC when the IPC determines that the system voltage is less than 11 volts.
SERVICE CHARGING SYSTEM - 102
The IPC illuminates the SERVICE CHARGING SYSTEM - 102 indicator in the DIC when the PCM detects a malfunction with the generator output. The IPC receives a class 2 message from the PCM requesting illumination.
