STARTER MOTOR CHECKS

TM 10-3930-644-14 & P

4. Pull starter out of flywheel housing until drive

end clears flywheel housing and tilt commutator

end up to remove unit from truck.

E. STARTER MOTOR CHECKS

With the starter motor removed from the vehicle, the

pinion should be checked for freedom of operation by

turning it on the screw shaft. The armature should be

checked for freedom of operation by turning the pinion.

Tight, dirty, or worn bearings, bent armature shaft, or

loose pole shoe screw will cause the armature to drag

and it will not turn freely. If the armature does not turn

freely, the motor should be disassembled for repair. If

the armature does operate freely, the starter motor

should be given a no-load test before disassembly.

1. No-Load Test

Connect the starter motor in series with a fully

Figure 3-2. No-Load Test Hookup It

charged battery of specified voltage, an

ammeter capable of reading several hundred

(2) Shorted armature.

This can be

amperes and a variable resistance.

Also

further checked on a growler after

connect a voltmeter, as illustrated in Figure 3-2.

disassembly.

An r.p.m. indicator is necessary to measure

armature speed. Obtain the specified voltage by

(3) Grounded armature or fields. Check

varying the resistance unit.

Then read the

further after disassembly.

current draw and the armature speed and

compare these readings with the values listed in

c. Failure to operate with high current draw

the starter motor specifications.

indicates:

Results of Test

(1) A direct ground in the terminal or

fields.

a. Rated current draw and no-load speed

indicates normal condition of the cranking

(2) "Frozen" bearings (this should have

motor.

been determined by turning the

armature by hand).

b. Low free speed and nigh current draw

indicates:

(1) Too much friction tight, dirty, or worn

bearings, bent armature shaft or

loose pole shoes allowing armature

to drag.

R-146-1

3-93