(1) The battery capacity is insufficient. (2) Faulty wiring contact (3) Burnt or greasy surface of the commutator. (4) Large wear of the carbon brush or insufficient carbon brush spring pressure caused poor contact between the carbon brush and the commutator. (5) Ablation of the main contract of the solenoid relay, faulty contract (6) Serious wear of the bearing, jamming of the armature with the housing
(1) Battery charge. (2) Tighten the wiring fastener (3) Grind the surface of the collector, remove dirt (4) Replace or adjust (5) Sand with non-metallic sandpaper marked “0” (6) Replace the bearing