... heat, noise, not broken, do not change color brush braid, no ablation. (4) is running, ... drawing or sample.Information for your reference Carbon brush performanceCommutator: Unit must be in good condition ... , or are worn, will cause excessive brush wear.Brush Holder Angles:The angles should be set ... set, you may experience excessive arcing, heating, brush wear, and commutator wear.Machine Neutral:To ...