Fan Failure.
Undo the three wingnuts holding the fan to the bottom of the combustion chamber, take off the electrical connection and white air hose, drop the fan housng and clean it out.
You can blow it with an air line, and if possible add some light oil to lubricate the shaft.
e-mail me on tremar@tinyworld.co.uk for further advice.
Ray Milner, December 2008