Testing Armature
for
Grounds:
Touch one ohmmeter
lead to a commutator bar and then touch the other lead
to
armature shaft and core laminations.
A
low resistance
reading indicates a grounded armature. Replace
grounded armature with a new part. See Figure
6-23.
ES-1614
FIGURE
6-23.
TESTING
ARMATURE
FOR
GROUNDS
Testing for
Shorts:Use a growler (Figure
6-24)for
locat-
ing shorts in the armature. Place armature in growler
and hold a thin steel blade (e.g. hacksaw blade) parallel
to
the core and just above the armature while slowly
rotating armature in growler.
A
shorted armature will
cause the blade to vibrate and be attracted to the core.
Replace a shorted armature with a new part.
.
ES-1615
FIGURE
6-24.
TESTING
ARMATURE
FOR
SHORTS
Testing for Opens:
Touch one ohmmeter lead to a
commutator bar and then systematically touch the other
lead
to
each
of
the remaining commutator bars.
A
high
resistance reading indicates an open circuit between
the commutator bars and armature windings. Replace
an
open
armature with a new part.
Brush Inspection:
Measure brushes (Figure
6-25)
and
replace
if
worn less than
0.425
(1 1
mm).
0.315
INCH
NEW
0.472
INCH
ES-1768
FIGURE
6-25.
BRUSH
INSPECTION
6-23
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