What is the function of the ignition sensor in a furnace and how does it contribute to the overall operation of the heating system?

The ignition sensor in a furnace is responsible for detecting when the pilot light or main burner flame is lit. It ensures that the fuel is ignited properly, allowing the heating system to function efficiently and safely. If the ignition sensor fails, the furnace may not start or stay lit, leading to a lack of heat in the home.