What a Flame Sensor Is and Why It Matters Published on February 26, 2017 Receiving your seasonal furnace maintenance helps keep your furnace working up to 30% more efficient and helps extend the life of your system. But things may still go wrong, and when they do, you might feel like there is always something else. This time it’s your heat exchanger, next time it’s your control board. Now you need to replace your flame sensor. What is a flame sensor, anyway? A flame sensor is an important safety feature on your gas furnace. During the ignition pattern, your gas furnace enters a process where a spark or a hot surface ignitor actually ignites the gas. Once the gas is ignited, the flame sensor produces a current of electricity. The electricity is quantified in micro amps. If the furnace’s control board doesn’t read the correct 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 impede the flame sensor’s ability to function properly, which can result in a malfunction of the furnace. The way to diagnose if a dirty flame sensor is causing a furnace malfunction is to take a micro amp draw reading, which an expert heating technician can provide you. If a dirty flame sensor is the reason, the furnace expert will clean the sensor with steel wool. If dirt was the single factor, we will see a notably higher amp reading. If the reading does not change, the technician will proceed with the heating system repair diagnostic process. If you aren’t certain your heating equipment is going to make it through these last few weeks of winter, give Service Experts Heating & Air Conditioning a call and we’ll come out and perform a full furnace maintenance or a free in-home estimate on a new HVAC system.