Brush sparks
In universal motors brush sparks are an inevitable occurence and a likely cause of radio and television interference. Built-in interference suppression components are normally used to prevent these disturbances. Slight sparking of a white to bluish colour is normal; however, the tool should be serviced at once if the colour and intensity of the sparks change. These are unfailing signs of impending motor damage whereas commutator flashover, i.e. rotary brush sparks are a sign of an already damaged motor.