What a Flame Sensor Is and Why It Matters Published on February 26, 2017 Setting up your annual furnace maintenance helps keep your heating equipment operating up to thirty percent more efficient and helps extend the life of the equipment. But things could still go wrong, and when they do, you might feel like you’re always hearing about something else. This time it’s your heat exchanger, next time it’s your control valve. Now you have to have your flame sensor replaced. What is a flame sensor, anyway? A flame sensor is a critical safety feature on your gas heating equipment. During the ignition sequence, your gas furnace enters a process where a spark or a hot surface ignitor will ignite the gas. As the gas is ignited, the flame sensor creates a current of electricity. This is calculated in micro amps. If the furnace’s control board does not read the right level of micro amps, the furnace will quit giving the system fuel to stop an explosion. Over time, if the flame sensor is not adequately cleaned, oxidation or carbon buildup can interfere with the flame sensor’s ability to operate properly, which can cause the furnace to malfunction. The way to diagnose if an unclean flame sensor is the reason for a furnace malfunction is to take a micro amp draw reading, which an expert heating technician can give you. If a dirty flame sensor is the reason, the furnace expert will clean the sensor with steel wool. If dirt was the sole factor, we will see a significantly higher amp reading. If the reading shows no change, the technician will continue with the furnace repair diagnostic process. If you aren’t certain your furnace is going to outlast these last few weeks of winter, give Service Experts Heating & Air Conditioning a call and we’ll come out and give you a full furnace maintenance or a free in-home estimate on a new furnace.