Field Coils

1. Using self-powered test light, place one test lead on field coil terminal strap, and touch other test lead to field coil brush lead (check series coils and shunt coils separately at appropriate terminals).
2. Lamp should light. If lamp does not light, coils are open. Check for grounds by placing one test lead on field armature strap, and touch other lead to armature core or shaft. If lamp lights, one or more coils are grounded.

Replace brushes if worn to 1/2 of original length, or if oil-soaked or pitted. Check brush spring tension and replace springs if weak or distorted. Deformed or bent brush holders can be replaced by service units which are installed with screws and nuts.