Be sure you have set the beater bar at the right height. If it's set too low, it will be hard to push, and the beater bar can't really work. Thick carpets need to be set at a high number, while uncarpeted floors need a low number
Be sure you change the bag regularly when it is about 3/4 full. The vacuum won't pick up dirt if the bag is too full. Slip the full bag directly into a plastic trash bag.
Changing the beater-bar belt when it wears out or breaks is simple and will save expensive repair bills. Here's how:
Figure A
Figure B
Figure C
Figure D
Figure E
Turn the vacuum head over and remove the four screws typically found on the underside (figure A). Check the manufacturers directions for your model.
Remove the wide beater bar (which will slip out easily), and the white motor (figure B).
Slip the new belt over the beater bar (figure C) and secure with the guard that holds it in place.
Hook the belt to the small end of the turbo motor (figure D) and re-insert back into the head of the vacuum. It should click into place.
Replace cover and screw into place.
While the cover is off, take a minute to clean the beater bar with a toothbrush and remove snarled threads with a pair of scissors run along the groove (figure E).