3 weeks ago, suddenly, the heater stopped working. A technician checked everything and told me that the control board had some glitch. He suggested me to replace the entire unit and the furnace, because Haier did not make the control board anymore. He pushed a button next to the board and did something else. Then, the heater was working again. He urged me to change the unit as soon as possible, for he was afraid the temporary fix would not last long.

Last night, around 9 PM, the air coming from the vent gradually becoming cooler. It took about 20 minutes for the warm air became cool air.

This afternoon, I pushed the button the tech did before. Magically, the heater worked again after that.

Tonight around 9 PM, the air from the vent started to turn cooler air again, as that of last night. Last night and tonight, the temperature reached down about 34 degree at 9 PM. I am starting to wonder if the heat becoming cool air has anything to do with outdoor temperature, or mainly the problem from the control board. Perhaps it's coincidence, but can anyone shed some light with me?