I have a combo heat and cooling system the problem is with the heat the unit cycles glow light comes on the furnace firers up and then shuts down I have to reset the system two maybe three times what causes this seem like every night I have to go through this what can it be

Have a combo heat and cooling system the problem is with the heat the unit cycles glow light comes on the furnace firers up and then shuts down I have to reset the system two maybe three times what causes this seem like every night I have to go through this what can it be