I have the Windtunnel 8000, and have had both issues at some point. The brushes will not rotate properly if the belts are not attached the right way, or in disrepair. They are very easily replaceable.
As for the lack of suction, you may have a blockage somewhere. I found two places where things clog up. If you flip over your vacuum, you can unscrew the plate that covers the brush. Take that off. I found another small plate attached with a single screw which leads to spot where the dirt actually gets sucked up. There is a flap there. It may be clogged with debris. Or, it may not be opening when the vacuum is engaged. I had the latter happen and it turned out that a part (I think it was a spring) needed to be replaced. I took it to a shop where they fixed that and apparently pulled out a large clog.
Because I refuse to pay someone to clean a clog, I found that if suction is a problem, I check the flap to see if it is blocked with debris. The other place I look is along the hose line at the back of the vacuum. You need to remove all the screws in the back with a special screwdriver (star shaped head). Once the screws come out, the back panel comes off. You can pull all sorts of gunk out of there. Just make sure you get the hoses reattached right when you put it back.
Overall, I'm disappointed in my vacuum, because I don't think you should need to go to this effort for maintenance. If it was a once a year unclogging, fine. But it is much more often than that.
Ilana, January 2005
