Unscrew the front panel, control panel and on the top left you'll see a black fan control unit (directly behind the vent on the inside of the door). There are two electrical connectors which you should detach (note which goes where - top right, bottom left). Detach the black feeder tube from the bottom and clean out. Then turn the black control unit anti-clockwise and it should detach from the inside vent. You'll probably see loads of crud/dirt/food around the join. This is a two part fan panel, unscrew and take apart. clean all the crud/dirt from around the black/white vent which sits in front of the actual fan. Reassemble and this should do the trick.
Robbo
June 2009