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TM 5-4210-220-12
4-24. ELECTRICAL SYSTEM - Continued
4-24.2 Starting Motor - Continued
Short circuits are located by use of a growler. When the armature is revolved in the growler, a metal
strip, such as a hacksaw blade, held above it will vibrate above the area of the armature core in which the short circuit is
located. Shorts between commutator bars are sometimes produced by brush dust or copper between the bars. These
shorts can be eliminated by cleaning out the slots. Replace armature if short cannot be removed.
Ground circuits are located by placing one test point of a 110-volt test lamp on the commutator bar with
the other point on the core or shaft. Replace the armature if a winding is grounded.
(24)
Check electrical continuity of the field coils. Connect a 110- volt test lamp between the field coil connector
and the field frame. If the lamp illuminates, at least one field coil is grounded.
(25)
Remove all coils and separately test each coil. Replace any falling inspection.
(26)
Connect test lamp leads to each field coil and check for an open circuit field coil. If lamp does not
illuminate field coins are open circuit.
(27)
Connect the solenoid circuit as shown. If the current reading is very high this indicates a shorted or
grounded hold-in winding. A very low reading indicates poor connections. Replace the solenoid if any
faults are indicated.
CAUTION
To prevent overheating of the winding, connect pull-in winding for 15 seconds only.
4-420
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