Charging Circuit-Theory Of Operation - Jacobsen AR-3 Technical/Repair Manual

ELECTRICAL
Charging Circuit—Theory of
Operation
With the engine running and the key switch in the run
position, current flows from key switch terminal AC
through 7.5-amp fuse F7 to the alternator field terminal,
exciting the alternator. With the alternator field terminal
excited, the alternator produces three-phase alternating
current (AC). The AC current is rectified by internal
diodes and direct current (DC) is available to the internal
voltage regulator.
When the battery voltage is low, current flows from the
voltage regulator to the battery, charging the battery.
When the battery is fully charged, the regulator stops
providing current to the battery.
Unswitched power is available to multi-function gauge
terminal 8 through 2-amp fuse F5.
With the key switch in the run position current flows
through 5-amp fuse F8 to multi-function gauge terminal
2, powering up the gauge. Voltage is also available from
4
fuse F8 to alternator light H6.
When the key switch is in the run position and with the
engine off, the voltage regulator detects zero output
voltage from the alternator and provides a ground to the
alternator light circuit. With the alternator light circuit
grounded, current flows through the alternator light,
turning on the light. Ground is also provided from the
voltage regulator to the multi-function gauge hour meter
enable input terminal. With the input terminal grounded,
the multi-function gauge is prevented from logging hours
on the hour meter.
When the engine is running, and the alternator is
operating correctly, the voltage regulator does not
provide ground to the alternator light circuit and the
alternator light is off. With the alternator light circuit not
grounded, voltage is provided to the multi-function gauge
hour meter enable input terminal through the filament of
the alternator light, activating the input. With the input
activated, the hour meter begins logging hours.
With the engine running, and when the voltage regulator
detects low output voltage from the alternator, the voltage
regulator provides a ground to the alternator light circuit.
This turns on the alternator light and the hour meter
stops logging hours.
4-24 4181384 First Edition