Indoor unit displays F9, often related to filter or air quality functions

Safety first: Turn off the unit before cleaning.

Steps:

• Clean filters: Remove and thoroughly clean all air filters. Reset the filter sign according to the user manual (often by holding a specific button on the remote).
• Check air quality sensor: On models with a dust/odor sensor, gently clean the sensor area with a soft brush. Ensure its connector is secure.
• Reset error: After cleaning, power cycle the unit and clear the error via the remote if required.
• Replace sensor: If F9 persists and the sensor is present, replace the air quality sensor module.