You could also have the off temperature set so low that the furnace never reaches that point. But the most likely situation is that the fan control is either on manual or the points have welded themselves together.: The blower on the furnace will not shut off. The only way to stop the fan is to interupt the power supply. Are there any suggestions on where I can start to look in order to repair this. Is it likely to be the thermostat. It is an automatic programable model.
