What must be done to generator brushes when they are replaced?

• A. Seat the brushes contour to fit the commutator
• B. Replace with standard lubricated brushes
• C. Polish or sand the brushes
• D. Tighten firmly to reduce wear

Answer: (A)

When generator brushes are replaced, the contact faces must be seated to fit the commutator. The commutator surface is curved, and a new brush starts out slightly different in shape. If you just install it without seating, contact is uneven, which can cause sparking, uneven wear, and poor current transfer. By seating the brush, you wear the brush face to mirror the exact contour of the commutator, producing even contact pressure across the surface and maximizing electrical transfer and brush life.

This is usually done by operating the generator at a low speed with light loading and gently guiding the brush so it wears in to the commutator’s curvature. Do not lubricate the brushes, and avoid polishing or sanding the brush faces, as altering their shape can ruin the fit. Also avoid over-tightening; the goal is proper seating and contact, not simply cranking down the hardware.