Furnace or ductwork produces a high-pitched whistling noise during operation.

Safety first: Turn off power before adjusting internal components.

• Filter type: Replace high-MERV or thick media filters with a Bryant-approved filter that matches the duct design.
• Open returns: Ensure all return grilles are unobstructed. Add additional return grilles if the system is starved for air.
• Check filter rack: Make sure the filter is fully seated and not being sucked into the opening, creating a whistle.

If whistling persists, a static pressure test by a technician can identify duct restrictions.