How do I change the belt on a Bissell Powerforce model 3522-1?

This is how you do it Lower handle and place vacuum on floor so you can see bottom of power head. Examine the power head to remember what it should look like when finished. Unscrew the four screws (Phillips screwdriver). Lift off cover. Lift out brush. Remove belt from brush and motor shaft. Place new belt around motor shaft, then around brush just prior to reinserting brush. Make sure the belt is placed correctly. Reinsert brush in slots. Rotate manually toward motor a few time to center the belt. Replace cover and screws. Tighten securely. Check cover to make sure it's properly secured.