Charging System: Description and Operation

OPERATION
The charging system consists of:
^ Generator
^ Electronic Voltage Regulator (EVR) circuitry within the Powertrain Control Module (PCM)
^ Ignition switch (refer to the Ignition System for information)
^ Battery (refer to the Battery for information)
^ Battery temperature sensor
^ Generator Lamp
^ Voltmeter (refer to the Instrument Panel for information)
^ Wiring harness and connections

DESCRIPTION
The charging system is turned on and off with the ignition switch. When the ignition switch is turned to the ON position, battery voltage from the ASD relay is supplied to the generator rotor and the current to produce a magnetic field is controlled by the PCM internal regulator. This is done through one of the two field terminals at the rear of generator.

The amount of DC current produced by the generator is controlled by the EVR (field control) circuitry contained within the PCM. This circuitry is connected in series with the second rotor field terminal and ground.

A battery temperature sensor, located in the battery tray housing, is used to sense battery temperature. This temperature data, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. This is done by cycling the ground path to control the strength of the rotor magnetic field. The PCM then compensates and regulates generator current output accordingly.

All vehicles are equipped with On-Board Diagnostics (OBD). All OBD-sensed systems, including the EVR (field control) circuitry, are monitored by the PCM. Each monitored circuit is assigned a DTC. The PCM will store a DTC in electronic memory for any failure it detects. Refer to On-Board Diagnostic Test For Charging System for more information.