TM 5-3810-307-24-1-2
Figure 2 Cross-sectional view, typical 37-MT motor.
A basic circuit of a 37-MT is shown
gear and the solenoid main
starts. A cranking period for all
in Figure 3.
contacts to close, and cranking
types of motors should never
takes place. When the engine
exceed 30 seconds without
For all circuits, when the start
starts, pinion overrun protects the
stopping to allow the motor to cool
switch is closed, the magnetic
armature from excessive speed
for at least two minutes.
switch contacts close, and the
until the switch is opened, at which
The 30-second limit also applies to
solenoid windings are connected to
time the return spring causes the
motors with a thermostat. If over-
the battery.
pinion to disengage. To prevent
cranking
should
occur,
the
excessive overrun and damage to
thermostat will open and the
The resulting plunger and shift
the drive and armature windings,
cranking cycle will stop to protect
lever movement causes the pinion
the switch must be opened
the motor.
After the cranking
to engage the engine flywheel ring
immediately when the engine
motor cools, usually 1-6 minutes,
the thermostat will close and then
a new starting attempt can be
made.
TROUBLESHOOTING THE
CRANKING CIRCUIT
If the cranking system is not per-
forming properly, make the
following checks to help determine
which part of the circuit is at fault.
Battery:
The battery is fully
charged. The wiring, switches,
and cranking motor cannot be
checked if the battery is defective
or discharged.
Figure 3 Basic cranking circuit (37-MT).
E-4 Change-1
