Mitsubishi diesel engines Service Manual page 173

ELECTRICAL SYSTEM - DISASSEMBLY, INSPECTION AND REASSEMBLY
Armature coil continuity
(e)
Measure between the commutator segment
and the armature coil. There should be no
continuity. If continuity is indicated, replace
the armature.
Armature coil open circuit
(f)
Measure between the segments in various
combinations. There should be continuity. If
no continuity, replace the armature.
Inspecting the field coils
(3)
(M008T70471A, M008T81071A)
There should be no continuity between the coil
(a)
end (brush) and the yoke.
There should be continuity between the coils
(b)
(brushes).
The pole-shoes and the coils should not be
(c)
loose. If faulty, replace the yoke.
Inspecting the bearings
(4)
Ensure that the bearings rotate smoothly without
abnormal noise. If faulty, replace.
Inspecting the rear bracket
(5)
If the metal is worn, replace the rear bracket.
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Testing the armature coil
Testing the armature coil for open circuit
Inspecting the field coils