AIRCARE digital humidifier displays an 'F' or 'FL' style code and will not run even though the tank appears to be installed.

Safety first: Turn the humidifier OFF and unplug it before inspecting the float or water level system.

• Step 1 – Remove the tank: Lift the water tank or bottle straight up and set it aside.
• Step 2 – Locate the float assembly: In the base of many AIRCARE console and tower humidifiers there is a plastic float or a magnetic float assembly that rises with water level.
• Step 3 – Check for free movement: Gently move the float up and down. It should move smoothly. If it is stuck, remove it (if removable) and soak in a 50/50 vinegar and water solution for 20–30 minutes to dissolve mineral deposits. Rinse thoroughly.
• Step 4 – Clean the float well: Wipe the float chamber and surrounding area with a soft cloth and vinegar solution to remove scale that may be binding the float.
• Step 5 – Verify magnet/sensor alignment: On models with a magnetic float and reed switch, ensure the float is installed in the correct orientation and fully seated so the magnet can trigger the sensor when water is present.
• Step 6 – Reinstall tank correctly: Fill the tank fully, ensure the cap is tight and the valve is not leaking, then place the tank squarely on the base. Many AIRCARE units require the tank to be perfectly aligned to depress an internal valve and satisfy the level sensor.
• Step 7 – Power up and test: Plug the unit back in and turn it ON. The F/FL code should clear once the float rises and the sensor detects water.

If the code persists with a free-moving float and full tank, the internal water level sensor or control board may be faulty and professional service or part replacement is recommended.