Brushes in the motor are badly worn causing the motor to short circuit either replace the brushes depends what type of motor you have or buy a new or recondioned one or you could remove the motor and check to see how badley they have worn down if the motor lookes sooty you then you have got carbon building up from the brushes causing the fault you can clean the motor and brushes with wd40 or with white spirit using a clean cloth make sure you give the motor a good clean i had this problem with my machine and its ok now and its still going and that was 2 years ago.
noel
September 2009