The weak link is usually the integrity of the mains cable. Over time it gets constantly stressed by pulling and little by little the connections get wrecked until the motor stops.
Your fault(s) may well be due to the motor(s) but it's easier, quicker and cheaper to check the power cable (and eliminate it) before anything so drastic as motor repair or replacement.
Next is on/off switch - then the motor.
Peccavi
January 2009