Remove the hose and turn it on - cover the air inlet hole with your hand and listen to the motor - that is the sound of a blocked hose - the motor will run faster and make a higher pitched sound.
Now fit the hose - if you hear the same high pitched sound you'll know you have a blockage in the hose. If the sound is more "normal" you may well have a split in the hose or a gap in the cleaning head where air is getting in.
You might also check and filters and bags the machine has.
Peccavi, November 2010
