When a vacuum cleaner is blocked the motor actually runs faster because it has no load - no air to move - if your machine's motor is making a higher pitched sound then it probably is blocked - but if you've lost suction it may well be because air is entering form a place where it should not be getting in. i.e. do not just search for a blockage - consider a split hose or a loose joint in an airway.
Good luck...
Peccavi, November 2010
