Diagnosis
Dust buildup on the intake grill and internal blades reduces airflow and efficiency. The rear grill is designed to be removed for cleaning.
How to Fix It
Unplug the fan. Lay it flat on a towel. Remove the several Phillips-head screws from the rear plastic grille. The grille will lift off, giving you full access to the fan cylinder and blades. Use a vacuum brush attachment and a damp cloth to clean everything.
If That Didn't Work
If the grille won't come off after removing screws, check for hidden plastic clips along the sides. Gently pry with a flathead screwdriver wrapped in cloth.
Heads Up
Do not spray cleaners or water directly into the housing. Moisture can damage the motor and electronics. Only wipe with a damp—not wet—cloth.