Hi appliantologists, I have the Trane XL80 with a Trane branded XT302A thermostat. Once in a while, the thermostat kicks on its System light, as it should do when the temperature drops below the desired level, but the XL80 ignores it and does not fire up. If I go to the unit and power down for a few seconds and then power it up, the furnace will behave as expected and fire up, heating the house. Any ideas as to what is going on when this happens?