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Armature Test

NOTE: Any ball bearings that are removed from armature must be replaced with new bearings.
  1. Inspect solder joints between armature windings and commutator bars. If any have come loose, replace armature. If commutator is rough or damaged, replace armature. DO NOT  turn commutator in lathe or undercut spaces between bars. If commutator is dirty, clean with fine grit emery cloth and blow away any copper dust.
  2. Using growler, check armature for shorts. Hold a flat steel strip on armature parallel to armature core or shaft. Rotate armature in growler. Steel strip will vibrate on area of short circuit.
  3. Using self-powered test light, place one lead on armature shaft and other lead on commutator. Test light should not illuminate. If test light illuminates, armature is shorted or grounded and must be replaced.
  4. If no-load test indicated armature may be rubbing against inside of frame and field assembly, inspect outside of armature for signs of rubbing. If armature is scored only on one side of laminations, armature shaft may be bent and armature should be replaced. If scoring is all around armature laminations, check frame and field assembly for an out-of-position pole or for a foreign object lodged inside. Repair or replace frame and field assembly.
CAUTION: Some starters have a molded-type commutator. DO NOT  undercut insulation as it may cause serious damage to commutator.
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