I have a new problem with my dual fuel gas furnace. I originally thought it was the defrost because it does it whenever I am leaving for work, or very late at night. Times I am not willing to go and check on it. But last night it stayed stuck after I turned the heat up, on a relatively warm night. I doubt it is the thermostat because it will not turn off unless I turn the unit off or put the thermostat between heat and off, it will still run if it put it in off. I am thinking it is the furnace control board.