My furnace will not keep the heat that it is set for. We've had multiple service guys look at the furnace and no one can tell me what the issue is. They changed the circuit board twice and the problem is still there. The blinking light on the furnace means that is is locked out for the hour. It should kick back on after that but usually it doesn't. If it does, then it will only heat up by half a degree. Does anyone have a possible solution for this issue as it is recurring every year.