I have a 15 year or older Day and Night Gas Furnace/AC. Ac worked no problem this past summer. Heater is blowing cold air. Pilot light stays lit. Changed the thermostat to a newer digital one. While cold air is being blown, I go on the roof, and on the left side of the thermocouple I turn the big black valve off for about a minute, then to on...and the burners fire up every time, and I have hot air. If I drop the temp between 62 and 70 the burners will not go on from the thermostat. Naturally I can't keep doing the roof thing. Any thoughts would be appreciated.
------------------------------------- Will Latorres