TM 5-3895-379-23
THEORY OF OPERATION - CONTINUED
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ELECTRICAL SYSTEM - CONTINUED
7.
Starter.
a.
The starter is used to turn the engine flywheel fast enough to start the compression/ignition process and make the
engine run. When the engine start switch is activated, voltage from the electrical system causes a solenoid to move
a pinion toward the flywheel ring gear of the engine. The electrical contacts in the solenoid close the circuit
between the battery and the starter just before the pinion engages the ring gear causing the starter to rotate. A
starter with this type of turn-on is known as a positive shift starting motor.
b.
When the engine begins to run, the overrunning clutch portion of the pinion drive prevents damage to the starter
caused by excessive speeds by breaking the mechanical connection. The pinion will stay meshed with the ring gear
until the engine start switch is released from the start position. A return spring in the overrunning clutch returns the
clutch to its rest position.
8.
Fuses. Fuses are safety devices which open an electrical circuit in the event of a short or malfunction to protect the sys-
tem from damage. A filament inside the fuse allows a measured amount of current to travel through the circuit. The fila-
ment disintegrates when too much current attempts to pass through the fuse. Once a fuse has "blown" it must be
replaced. Fuses are provided for each of the major system circuits.
9.
Engine Start Switch. The engine start switch is a rotary key-type switch that turns the electrical system on or off and
activates the starter. When the start switch is turned to the start position (held to far right), electricity is sent through the
neutral start and main relays. After these relays, the electricity then goes to the starter.
10.
Starter Relay. The starter relay allows electricity to flow to the starter when the engine start switch is in the start posi-
tion.
11.
Neutral Start Relay. The neutral start relay is a safety device that stops the flow of electricity to the starter when the
propel control lever is set in a position other than neutral.
12.
Lights Circuit Breaker. The lights circuit breaker is a heat-triggered switch that opens the lights circuit when the cur-
rent in the electrical system goes higher than the rating of the circuit breaker (20 amps). Push the reset button to close
the circuit again.
13.
Main Relay. The main relay allows electricity to flow to all circuits only when the engine start switch is in the acces-
sory, run or start positions.
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