My wife and I bought our first house together about 6 months ago and this is our first winter in it. Living in East Texas, it doesn't get that cold often but we just noticed the other night that our thermostat was off as my wife wanted the heater on. I went out and took the panels off the unit and found that on the lower circuit panel the breaker(on the unit itself) was tripped. I reset it which turned the unit back on. I watched after a few minutes as the variable speed fan came on and then what sounded like the compressor and then a small black box on the board that has power to it and small copper wire wound around the back of it makes a noise and then it trips. I hope that this is enough information for you who know much more about these units than myself.