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 DISABLING & ACTIVATING AIR BAG SYSTEM 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 AD237, CS130D and Bosch NCB1 generators have high amperage output. See GENERATOR SPECIFICATIONS . Generators include a delta stator, rectifier bridge, and rotor with slip rings and brushes. A built-in regulator incorporates fault detection circuitry. A conventional pulley with (external) fan is used to cool slip ring and frame. The "D" indicates dual internal fans designed to cool rectifier bridge and regulator.

Generator provides voltage to operate vehicle's electrical system and to charge its battery. A magnetic field is created when current flows through rotor. This field rotates as rotor is driven by engine, creating an AC voltage in stator windings. AC voltage is converted to DC by rectifier bridge and is supplied to electrical system at battery terminal.

When engine is running, generator turn-on signal is sent to generator from PCM, turning on regulator. Generator's voltage regulator controls current to rotor, thereby controlling output voltage. Rotor current is proportional to electrical pulse width supplied by regulator. When engine is started, regulator senses generator rotation by detecting AC voltage at stator through an internal wire. Once engine is running, regulator varies field current by controlling pulse width. This regulates generator output voltage for proper battery charging and electrical system operation. Generator F terminal is connected internally to voltage regulator and externally to PCM. When voltage regulator detects a charging system problem, it grounds this circuit to signal PCM that a problem exists. PCM monitors generator field duty cycle signal circuit. System voltage sense circuit receives battery positive voltage that is hot at all times through a fuse link that is connected to starter motor. This voltage is used by regulator as reference for system.

Regulated voltage varies with temperature. System limits voltage by controlling rotor field current while field current is on. Regulator switches rotor field current on and off at a fixed frequency of 400 cycles per second to help control radio noise. By varying overall on-off time, correct average field current for proper system voltage control is obtained. At high speeds, with lower electrical loads, on-time may be 10 percent. At low speeds, with higher electrical loads, on-time may be as much as 90 percent.