(2) Testing Armature.
(c) Testing Amature for Open Coils. Test coils
indicates open coil.
Touch armature shaft and the end of each commutator bar
with a pair of ohmmeter leads. There should be no conti-
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,
(b) Testing Armature for Shorted Coils
to test for shorted coils.
(e) Testing Armature Shafl Runout
With the armature in the growler, turn the growler on and
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
slightly and repeat the test. Do this for one complete revo-
lution of the armature. If the armature has a short, replace
(3) Testing Field Coils.
(a) Using a test lamp and probes, check the
field coils for grounding to the motor frame or open