When I first turn on the heat, the gas furnace lights up appropriately, it heats and then the fan turns on and blows the warm air. After about 1-2 hours, the air is still blowing but it is now cold air. In order to get it hot again I turn the breaker to the furnace on and off and the cycle starts over again. Is the board the issue? Is the furnace overheating? It is a 1995 York furnace.

I am having the same problem with a Trane. I have been told to clean the thermocouple with sandpaper or scotchbrite. I plan on giving that a try tomorrow. The soot insulates it and the furnace thinks the flame went out so it shuts off the gas. What doesn't make sense to me is why it would run for so long before it shuts off. I (like you) have to turn the switch off and back on again for it to heat. Good luck!

Did you ever resolve your issue? I am having the same problem.

Any luck fixing this problem? I am having the same issue

Same problem here as well. Is there a wire I can cut that stops it from cooling the house down after it gets heated.. it seems my furnace is blowing in a constant chase of the set level of temperature... I don't want this, I want it to warm up and then cut off.. my house is like a sieve so it will cool on its own naturally. I am just wasting energy here am I not?