Parts Replacement & Testing: Armature

Check for shorted armature coils in a growler. Check for grounded coils by touching one test light probe to armature shaft and other probe to each commutator bar. Lamp should not light. If lamp lights, armature coils are grounded and armature should be replaced. Commutator should be smooth and clean, runout must not exceed 0.004". If runout is excessive, reface in a lathe removing only sufficient material to provide smooth even surface.