I have a carrier furnace that is ten years old. The last couple of days the heater has been turning on and off and temperature set never reach. The cycle was shorter and the heater was on and off one cycle continuous with the next. We look at the LED light and it wasn't flashing any code. We figure it's the filter problem because it was dirty and it was installed in the wrong direction. I wonder if this is it and if there is any things could cause short cycling ? We also replace new batter in the thermostat and all the connection to the thermostat is in place. After changing the filter... the cycle is longer and have short break in between. However... at night... it keeps running though!