Troubleshooting - Komatsu 830E Shop Manual

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 keyswitch, magnetic
switches, solenoids and cranking motor(s).
Clean, repair or tighten as required.
If the above inspection indicates the starter motor to
be the cause of the problem, remove the motor and
perform the following tests prior to disassembly to
determine the condition of the motor and solenoid
and repairs required.
Preliminary Inspection
1. Check the starter 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 starter
should be disassembled immediately.
3. If the armature can be rotated, perform the No-
Load Test before disassembly.
No-Load Test
Refer to Figure 2-7 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.
D02023
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, current,
and voltage reading to the following specifica-
tions:
Interpreting Results of Tests
1. Rated current draw and no-load speed indicates
normal condition of the cranking motor.
2. Low free speed and high current draw indicates:
a. Too much friction; tight, dirty, or worn bear-
b. Shorted armature. This can be further
c. Grounded armature or fields. Check Further
24 VDC Electric Supply System
FIGURE 2-7. 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
ings, bent armature shaft or loose pole
shoes allowing armature to drag.
checked on a growler after disassembly.
after disassembly.
D2-15