A furnace flame sensor is a small device that plays a crucial role in the safe operation of a furnace. It is a safety component that is designed to detect the presence of a flame in the furnace and ensure that the gas valve is only opened when a flame is present. If the flame sensor furnace is not functioning properly, the furnace may not operate correctly, or it may not operate at all. https://www.partshnc.com/furnace-parts/flame-sensor