7. Check the mica depth (A). If the mica is too high (B),
undercut the mica with a hacksaw blade to the
proper depth. Cut away all the mica (C) between
the commutator segments. The undercut should
not be too shallow, too narrow, or V-shaped (D).
Commutator Mica Depth
Standard (New): 0.4 0.5 mm (0.016 0.020 in.)
Service Limit:
0.15 mm (0.006 in.)
D
B
8. Check for continuity between the segments of the
commutator. If an open circuit exists between any
segments, replace the armature.
9. Place the armature (A) on an armature tester (B).
Hold a hacksaw blade (C) on the armature core.
If the blade is attracted to the core or vibrates while
the core is turned, the armature is shorted. Replace
the armature.
C
A
10. Check with an ohmmeter that no continuity exists
between the commutator (A) and armature coil
core (B), and between the commutator and
armature shaft (C). If continuity exists, replace the
armature.
B
A
C
B
C
A
(cont'd)
4-11