DIAGNOSIS Dust has accumulated on the sealed main bladewheel, which is not designed for user cleaning. This can happen over years of use.
FIX You cannot directly clean the sealed bladewheel. Use the machine's built-in cleaning function. Power the unit on. Press and hold the 'Oscillation' button and the 'Night Mode' button simultaneously for 10 seconds. All icons will illuminate. The fan will run at high speed for two minutes to dislodge dust from the internal mechanism. Perform this monthly.
IF THAT DIDN'T WORK For external dust, clean the intake grilles at the base with a soft, dry brush or a vacuum cleaner hose attachment. Ensure the pre-filter in the main filter assembly is not clogged—replace the main filter if it is old.
HEADS UP Do not attempt to open the main body or remove screws. This will void your warranty and can damage the sealed system. If internal dust buildup is severe and affecting performance, contact Dyson for a professional service check.