Heater runs fine for a full cycle for up to ten minutes or so then shuts off before it reaches the heat setting (set to 70 degrees, never gets above 65). Heater turns off and doesn’t come back on for quite awhile- not quick enough to get back to set tempI have replaced the thermostat and cleaned the heat sensor.1) Heat call from the thermostat. 2) Control board does a safety check (limit switches, roll out switches). 3) Inducer motor comes on. 4)Pressure switch must close to go to the next step. 5)Hot surface ignitor begins getting hot / direct spark ignitor begins to spark 6) Gas Valve opens 7)Furnace Lights 8)Flame Sensor senses flame 9) blower motor comes on. 10) Once thermostat is satisfied, the burner shuts offIt appears to be failing at 10- the burner is shutting off before the thermostat is satisfied. It might also be failing at 2)? Since the thermostat isn’t satisfied, I would expect a call much quicker. But it doesn’t come quick.So this sounds to me like there’s an overheating being detected. I’ve changed the air filter (which was the worst I’ve seen it- I normally change in spring and fall- I may have missed this fall) all my vents are open, the house hasn’t changed size (lol). But I’m thinking maybe the blower is dirty, or the sensor switch is bad? via /r/DIY http://bit.ly/2CJ8RzJ
