No suction may also be down to an air leak - split hose for instance.
It's just a fan in a box with holes for the air to come in and to go out.
Remove the hose and let the machine run - cover the hole with your hand and feel the suction - the motor will run noticeably faster - should run noticeably faster.
Fit the hose - if the motor runs faster again then the hose is blocked - if it runs with a lower pitched sound then air is entering the hose somewhere where it shouldn't.
Good luck...
Peccavi
January 2010