4-34 4203781 First Edition
ELECTRICAL
4
Charging Circuit—Theory of
Operation
Unswitched Power Circuit
Unswitched power is available from the battery positive
terminal to the starter motor battery terminal and then
from the starter motor battery terminal to 50-amp circuit
breaker (F1) battery terminal. Unswitched power is
available through the 50-amp circuit breaker (F1) to
30-amp circuit breaker (F2) input terminal and from
circuit breaker (F2) input terminal to 10-amp circuit
breaker (F5).
Unswitched power is available from circuit breaker (F2)
output terminal to accessory relay terminal 30.
Unswitched power is provided from 10-amp circuit
breaker (F5) to PTO switch terminal E.
Unswitched power is also available from the starter motor
battery positive terminal to the battery terminal of 50-amp
circuit breaker (F3). Circuit breaker (F3) provides
protection to the alternator battery terminal.
Interlock Circuit
The interlock circuit provides 12 volts to the key switch.
The following must occur before the key switch is
provided with 12 volts:
• PTO switch in the off position
• Park brake switch in the on position
With the PTO switch in the off position and park brake
switch in the on position, voltage is provided from the
park brake switch to key switch terminal B.
Charging Circuit
When the key switch is turned to the run position, voltage
is provided from key switch terminal I to accessory relay
terminal 86, energizing the relay. With the relay
energized, switched power is provided from accessory
relay terminal 87 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.