i replaced the filters but the replacement filter light won't turn off on my coway mighty.

Diagnosis

The "Check Filter" indicator on the Coway Airmega AP-1512HH Mighty is not a smart sensor that detects the physical cleanliness of the HEPA or carbon filters. Instead, it is a simple chronological timer that tracks the cumulative hours of operation. Once the unit reaches a predetermined threshold—typically around 12 months of standard use—the light triggers to notify the user that the filters are likely saturated.

Because the system does not have an optical or pressure-drop sensor to "see" the new filter, the light will remain illuminated indefinitely until the internal logic board is manually told to restart the countdown. If you have replaced the filters but the light persists, it simply means the reset command was not registered by the control panel. This is a common point of confusion, as users often expect the light to turn off automatically upon the closing of the filter door or the detection of airflow.

How to Fix It

To clear the filter alert and restart the 12-month timer on the AP-1512HH, follow these precise steps:

1. Ensure the unit is plugged into a grounded AC outlet and the main power switch is in the "ON" position. The unit must be powered on for the reset command to be processed.
2. Locate the "Filter Reset" button on the top control panel. On the AP-1512HH model, this is typically a smaller button located near the Fan Speed and Mode selectors.
3. Press and hold the "Filter Reset" button firmly for a full 3 to 5 seconds. Do not simply tap the button; a momentary press will not trigger the reset.
4. Watch the "Check Filter" LED indicator. Once the light turns off or flashes and then disappears, release the button.
5. Verify that the unit is now operating in its normal mode (Auto or Manual) and that the red alert light is completely extinguished.

If That Didn't Work

• Perform a Hard Power Cycle: Unplug the unit from the wall outlet for at least 60 seconds. This drains the capacitors on the control board and clears temporary logic glitches. Plug the unit back in and immediately attempt the 5-second hold on the Filter Reset button again.
• Check for Button Obstructions: Ensure that no dust or debris has lodged itself around the edge of the Filter Reset button, preventing it from making a full tactile connection with the internal switch. Use a can of compressed air to clear the gap around the button.
• Verify Control Panel Responsiveness: Test if other buttons (like the Fan Speed button) are responding. If the entire panel is unresponsive, the issue may be a blown internal fuse or a faulty control board rather than a simple filter timer issue.
• Sequential Reset: In some rare firmware versions of the Mighty series, you must first set the unit to "Eco Mode" before the Filter Reset button becomes active. Switch to Eco Mode, then attempt the long-press reset.

Heads Up

• Pre-filter Maintenance: The "Check Filter" light refers to the HEPA and Carbon filters. However, you should vacuum the external pre-filter (the plastic mesh) every 2-4 weeks to prevent the internal HEPA filter from clogging prematurely.
• Avoid Washing HEPA Filters: Never attempt to wash or vacuum the pleated HEPA filter or the activated carbon filter. Doing so destroys the electrostatic charge and the porous structure, rendering the filter useless even if the light is reset.
• Filter Seating: Ensure the new filters are seated flush against the internal housing. If there is a gap, air will bypass the filter (blow-by), and your air quality will not improve despite the reset light being off.
• Genuine Parts: Using non-OEM filters can sometimes lead to incorrect airflow patterns which may cause the unit to overheat, though this will usually trigger a different warning light than the filter reset indicator.