TM 5-3805-280-24-1
Sub-System Diagnostics
CHARGING CIRCUIT OPERATIONAL
INFORMATION
The following conditions must be met for the circuit to
function:
Key switch ON
Voltage present at alternator G3 terminals B+ and D+
Engine running
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CHARGING CIRCUIT THEORY OF OPERATION
9015
at alternator terminal D+ drops below 6 volts, as a
The charging circuit includes batteries, key switch,
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8
result of a charging circuit failure or the engine not
alternator shut down relay, alternator excitation
running, the monitor controller will turn on the
resistor, alternator shutdown relay and isolation diode,
alternator voltage indicator light and sound the display
monitor controller and display.
alarm.
With key switch S1 ON, battery power is applied
Once the monitor controller senses that the engine is
through alternator power 60-amp fusible link F22 to
running (voltage at alternator terminal D+ is greater
terminal B+ of alternator G3. Alternator excitation
than 10 volts), monitor controller and display terminal
power is applied from key switch S3 terminal M
18 is grounded. This provides a ground path for
through alternator shut down relay isolation diode V2
alternator shutdown relay K1, energizing the relay.
and alternator excitation resistor R6 to alternator
With relay K1 energized, battery power is applied
terminal D+. The excitation voltage is monitored by
through contacts 3 and 5 to alternator excitation
controller and display monitor A5 at terminal 42.
resistor R6. This ensures that power to the alternator
excitation circuit (and the alternator voltage output) is
With the engine running and the charging circuit
maintained as long as the engine is running, even if
functioning properly, the voltage at alternator terminal
the key switch is turned to OFF or ACC momentarily.
D+ is greater than 10 volts, therefore, alternator
voltage indicator light H18 and monitor controller and
Isolation diode V2 isolates the battery power at
display alarm H8 are off. Output current from alternator
terminal 5 of relay K1 from the key switch ON power
terminal B charges the batteries as needed and
circuits.
provides power to the machine circuits. If the voltage
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