GM Service Manual Online
For 1990-2009 cars only

General Description

    • The CS-type generator uses a internal regulator, which features built in fault detection. The generator used on this vehicle is not meant to be disassembled for service. If the generator becomes inoperative, the generator must be replaced
    • The CS generator uses a delta stator, rectifier bridge, and a rotor with slip rings and brushes. A pulley and a fan are used to cool the slip ring end frame, the rectifier bridge and the regulator.
    • This generator may be used with only two connections: the Bat terminal to the battery positive and the L terminal to the charge indicator. The use of the P, F and S terminals is optional. The P terminal is connected to the stator and is connected externally to a tachometer or other device.
    • The F terminal is connected to the field lead through the PCM and can be used as a system monitor.
        As the generator load increases, the PCM can adjust the idle speed accordingly.
    • In this type of circuit, the L can be used to energize the generator. The S terminal may be connected externally to a voltage, such as battery voltage, in order to sense the voltage to be controlled. Refer to Starting and Charging Schematics for complete schematics of the charging system.
    • As on other charging systems, the charge indicator on the instrument panel will light, with the ignition switch on, and the engine not running.
        When the engine starts, the indicator light should go out.
        If the indicator comes on and stays on with the engine running, there is a problem in the charging system. The indicator will glow brightly, no matter what problem it detects.
        The indicator will also come on with the engine running, if the system voltage is too high or too low.
    • The regulator voltage setting varies with the temperature. It limits the system voltage by controlling the rotor field current while the field current is on. This regulator actually switches the rotor field current on and off at a fixed frequency of about 400 cycles per second to help control radio noise.
    • By varying the overall on/off time, the correct average field current for the proper system voltage control is obtained. At high speeds, the on-time may be 10 percent and the off-time 90 percent. At low speeds, with high electrical loads, the on time may be 90 percent and the off-time 10 percent.
    • No periodic maintenance of the generator is required.