TM 5-3805-258-24-1
OPERATOR’S STATION
SYSTEMS OPERATION
INDIVIDUAL CIRCUIT DESCRIPTION
The magnetic fields, from the hold-in windings and from the pull-in wind-
ings, add together and start to move the plunger in the cylinder. The shift lever,
which is connected to the plunger, starts to move the pinion gear toward the ring
gear. The current, that goes through the pull-in windings and the starter motor
windings, makes the motor, and therefore the pinion, start to turn slowly so that
it engages correctly with the ring gear. When the plunger has moved far enough
to engage the pinion with the ring gear, it also makes contact between the switch
contacts and sends much current from the battery to the starter motor to turn it
very fast.
With the solenoid switch contacts closed, there is a short across the pull-in
windings and no current goes through them. Only the hold-in windings keep the
contacts closed and the pinion engaged with the ring gear.
When the start switch is released, the start solenoid opens and there is no
current through the hold-in windings from the start relay. The pull-in windings
are no longer shorted. For a very short time, current is sent from the motor
contacts, through the pull-in windings in a reverse direction and on through the
hold-in windings in the normal direction to ground. The magnetic fields made
by the two coils are opposite to each other and are cancelled out. The spring load
on the plunger moves the plunger back to the original position. This moves the
pinion away from the ring gear; it also opens the switch contacts so that current
is not sent to the starter motor.
3-171
