Vacs often have an overheat cut out for when the motor gets too warm - strapped to the motor - they usually self reset - yours may be defective, the on/off switch may be broken, the motor or its brushes may be defective or - the fault I have seen most often (50%) - continual stress in the power cable has caused it to break one of the conductors - usually at the wall plug end.
I can't imagine any vacuum cleaner having an internal fuse.
Good luck...
Peccavi, December 2009
