Take out the old belt
When your vacuum starts to lose cleaning power, requiring multiple passes to get an area clean, or the self-propulsion loses its zip, chances are you need to change the vacuum agitator belt. After only a few months of use, most vacuum belts stretch out enough to slip, causing the agitator to spin more slowly.
Replacing the belt is quick and inexpensive. New belts are available from a vacuum parts supplier (check online for a store in your area). Belts come in numerous brands and sizes, so bring the old one to the store for a guaranteed match.
Fifteen minutes, two screwdrivers and a new belt are all you'll typically need to complete the job. Photo 1 shows how to access the old belt. The cover on your vacuum may be held on by other arrangements of clips and screws.
After removing the cover, install the new belt as shown in Photos 2 and 3. Once the new belt's on and the agitator's back in place, turn the agitator by hand to make sure the belt spins smoothly, without rubbing or binding. Reassemble the bottom cover and test-run the machine.