Diagnosis
The filter life indicator is triggered by a timer, not actual sensor data. The unit tracks runtime and illuminates the red filter light at the preset interval.
How to Fix It
Reset the filter timer. Press and hold the 'Filter Reset' button on the control panel for 5 seconds. The red filter light will turn off. Confirm the pre-filter is clean and the HEPA filter is not physically damaged or clogged with debris.
If That Didn't Work
The filter reset button may require multiple attempts. Ensure you are holding it for the full 5 seconds. If the light persists, unplug the unit for 2 minutes, then plug it back in and attempt the reset sequence again.
Heads Up
The factory-set filter timer is conservative. If you use the unit in a heavily polluted environment, you may need to replace the filter before the light comes on. Visually inspect the HEPA filter through the side grille for deep discoloration.