What should I do when the Clean indicator light turns red?

The red Clean LED indicates it is time to clean the transducer/ultrasonic membrane to remove water mineral deposits. Clean the transducer/ultrasonic membrane with a 50/50 mix of white vinegar and water on a cotton swab, then wipe off with a damp cotton swab. After cleaning and refilling the tank with water, press and hold the clean indicator/reset button until the red LED turns off.