DIAGNOSIS A sustained high-pitched whine is almost always air leakage. The cyclone assembly seals or the bin O-ring are the most common failure points.
FIX Dismantle the vacuum. Remove the bin and clear-view cyclone by pulling up on the red release tab. Inspect the large purple O-ring at the base of the cyclone. Remove it, clean it with water, and dry thoroughly. Re-seat it carefully in its groove. Reassemble, ensuring a firm click.
IF THAT DIDN'T WORK Check the pre-motor filter. Remove it, wash with cold water only, and let it dry for 24 hours minimum. A clogged filter forces the motor to work against higher resistance, increasing pitch.
HEADS UP Never use detergents or hot water on the filter. Never run the vacuum without all filters correctly installed. This can cause permanent motor damage.