When first turned on, the power button starts at high (red) for a few minutes, then automatically drops to low (white). Blue medium. The heater was good, I wore it under my jacket. When the battery died and I replaced it with another, the power button immediately flashed blue and I didn't touch it. The button didn't respond at all at that moment and wouldn't turn off or on. It then gave off minimal heat and stopped working altogether shortly after. Same sequence of events on next docking, but with a shorter initial heat cycle. Big disappointment. The sweatshirt is of good quality, too bad it didn't fit. $130 buys a lot of body warmers!