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Commutator Test

  1. Ensure continuity exists between any 2 commutator segments. If continuity does not exist, replace armature.
  2. Clean commutator segment surfaces with No. 400 grit sandpaper (if necessary). If surface is scored, out-of-round, or pitted, replace commutator.
  3. Using "V" blocks and dial indicator, ensure maximum commutator runout and minimum commutator diameter does not exceed specifications. See STARTER SPECIFICATIONS .
  4. Standard undercut depth for insulating mica should be .016-.024" (.40-.60 mm). Minimum mica undercut depth is .008" (.20 mm). If depth is not within specification, replace armature.