Hi, If you look at the bars going across the front,under the second one down in each corner ia a screw. Undo them and pull the front away. You will see a rotary fan unit which blows air up across the strips of material. Try vacuuming the fan unit and gently the material strips. If that doesnt work you may need a fan replacement part - good luck with that if that is the problem!
IANB, November 2006