Figure 7-82. Testing Armature for Grounds

TM 9-2330-356-14

(2) Testing Armature.

(c) Testing Amature for Open Coils. Test coils

(a) Testing Armature for Grounds (Fig. 7-82).

indicates open coil.

Touch armature shaft and the end of each commutator bar

with a pair of ohmmeter leads. There should be no conti-

(d) Tessting Commutator Runout (Fig. 7-84).

nuity. If continuity is indicated between any commutator

Place armature in a test bench and test runout with a dial

bar and shaft, it indicates a grounded armature. Replace

indicator. When commutator runout exceeds 0.004-inch,

starter.

replace starter.

Figure 7-82. Testing Armature for Grounds.

Figure 7-84. Checking Commutator Runout.

(b) Testing Armature for Shorted Coils

(Fig. 7-83). A growler is necessary to test for shorted coils.

(e) Testing Armature Shafl Runout

With the armature in the growler, turn the growler on and

(Fig. 7-85). Place armature in a test bench and check shaft

run a steel strip (such as a hacksaw blade) over the arma-

runout with a dial indicator. If the shaft is bent or worn,

ture surfaces. If a coil is shorted, the steel strip will be-

starter must be replaced. Runout should not exceed

come magnetized and vibrate. Rotate the armature

0.006-inch.

slightly and repeat the test. Do this for one complete revo-

lution of the armature. If the armature has a short, replace

starter.

Figure 7-85. Checking Armature Shaft Runout.

(3) Testing Field Coils.

(a) Using a test lamp and probes, check the

field coils for grounding to the motor frame or open

Figure 7-83. Testing Armature for Shorted Coils.

circuit.