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CRANKING MOTOR TROUBLESHOOTING
If the cranking system is not functioning properly,
check the following to determine which part of the
system is at fault:
Batteries -- Verify the condition of the
batteries, cables, connections and charging
circuit.
Wiring -- Inspect all wiring for damage or
loose connections at the key switch,
magnetic switches, solenoids and cranking
motor(s). Clean, repair or tighten as
required.
If the above inspection indicates the cranking motor
motor to be the cause of the problem, remove the
motor and perform the following tests prior to disas-
sembly to determine the condition of the motor and
solenoid and repairs required.
Preliminary Inspection
1. Check the cranking motor to be certain the
armature turns freely.
a. Insert a flat blade screwdriver through the
opening in the nose housing.
b. Pry the pinion gear to be certain the arma-
ture can be rotated.
2. If the armature does not turn freely, the crank-
ing motor should be disassembled immediately.
3. If the armature can be rotated, perform the No-
Load Test before disassembly.
No-Load Test
Refer to Figure 2-5 for the following test setup.
Be certain switch is open before connections or
disconnections are made during the following
procedures.
1. Setup the motor for test as follows:
a. Connect a voltmeter from the motor terminal
to the motor frame.
b. Use an RPM indicator to measure armature
speed.
c. Connect a carbon pile across one battery to
limit battery voltage to 20 VDC.
D2-12
Do not apply voltages in excess of 20 volts.
Excessive voltage may cause the armature to
throw windings.
d. Connect the motor and an ammeter in series
e. Connect a switch in the open position from
2. Close the switch and compare the RPM, cur-
rent, and voltage reading to the following speci-
fications:
24 VDC Electric Supply System
FIGURE 2-5. NO-LOAD TEST CIRCUIT
with two fully charged 12 volt batteries.
the solenoid battery terminal to the solenoid
switch terminal.
RPM: 5500 Minimum to 7500 Maximum
AMPS: 95 Minimum to 120 Maximum
VOLTS: 20 VDC
D02034
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