These heaters have a thermostatically controlled safety switch. It works very similar to your household iron for pressing clothes. On your iron, when the unit heats up the metal in the switch expands and "clicks" open stopping the power from heating up the element any more, then when it cools down it "clicks" closed and power is applied to the heating element again. Now here is the problem... in your heater, the elements are over-heating and causing the safety switch to "click" open stopping ALL power from going to the unit. IF you sit there long enough, you will eventually hear the "click" of the switch cooling down and then you will be able to turn it back on for a short time - then it will do it all over again. =( Unfortunately, this seems to be a common problem with this series of heater. There really is no "good" repair option as the price you will pay for someone to "fix" it, would probably be better spent going towards a new heater.