Alternator Output

The PCM keeps charging system voltage at 13.5-14.8 volts. Charging system voltage will be adjusted by PCM based on battery temperature sensor, located within PCM housing. The voltage determined by PCM as final goal for charging system is called "control" voltage. The control voltage will be used to determine alternator field control and to detect if charging system is operating properly.

If sensed voltage is lower than "control" voltage, PCM will alter duty cycle and ground alternator (rotor) field for a longer period of time and create a higher alternator output which should raise sensed voltage level. If sensed voltage is higher than "control" voltage, PCM will alter duty cycle and lower alternator output which should lower sensed voltage level.