My wife just went in as we speak and shouted that our temp was flashing. For the arctic line, it is due to the temp being above what you set it to. For example we have ours set to 98 right now due to the hot summer. The heat causes the water to get warmer and once it goes 2 degrees over your selected temp, it flashes to let you know you tub has shut itself down. No filtering or heating goes on at this point.