Check the filter and make sure that it isn’t cracked, bent or torn. If the filter is in good condition, remove the filter and check the water reservoir for a plastic black cover about 1″ x 2″. With a flashlight, from above the filter opening, look to see if anything is blocking the path. Look thru the front grill starting at the top right hand corner about 1/3 of the way down. You will see a box that is 1″ x 1″ X 2″ attached to the coils, this is the sensor box. Make sure that the box has a cover. If you find the cover inside where the filter goes or in the water reservoir use the pictures provided to reattach the cover and box to its proper location on the coils.