Frequently Asked Questions What does it mean if the SENSEO CALC light is on? The CALC light turns on or starts blinking when it is time to descale your SENSEO coffee machine. This indicator light can only be turned off after successfully completing the descaling cycle. Why should I descale my SENSEO? There are several reasons why descaling your SENSEO is important: It prolongs the life of your SENSEO coffee machine It ensures maximum cup volume It ensures maximum coffee temperature Your SENSEO will produce less noise during brewing It prevents malfunctioning You can find instructions on how to descale your SENSEO in the user manual that came with your appliance.