There is a screen filter located on the very bottom of the cleaner that can be pulled out and cleaned. It is usually a red color. They get full of lint and restrict airflow to the turbine.
If this doesn't work, it is most likely that your turbine has failed. I have seen this happen numerous times to the newer Hoovers. Replacing it involves dismantling the base assembly and changing the turbine unit. If you are feeling adventurous, send me an e-mail for replacement information at arctic@worldlynx.net.
Help Around the House, May 2006