What a Flame Sensor Is and Why It Matters Published on February 26, 2017 Scheduling your seasonal furnace maintenance helps keep your heating system working up to 30% more efficient and helps extend the life of your system. But things could still stop working, and when they do, you might feel like it’s always something else. This time it’s your heat exchanger, next time it’s your control valve. Now you need to replace your flame sensor. By the way – what is a flame sensor? A flame sensor is a critical safety element on your gas heating equipment. During the ignition sequence, your gas furnace goes through a process where either a spark or a hot surface igniter will actually ignite the gas. As the gas is ignited, the flame sensor creates a current of electricity. This is quantified in micro amps. If the furnace’s control board fails to 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 cleaned appropriately, oxidation or carbon buildup can hinder the flame sensor’s ability to work properly, which can cause the furnace to malfunction. The way to determine if an unclean flame sensor is causing 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 culprit, 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 shows no change, the technician will carry on with the furnace repair diagnostic process. If you aren’t sure your furnace is going to make it through these last few weeks of winter, give Hammond Plumbing & Heating a call and we’ll come out and provide you with a full furnace maintenance or a no-charge in-home estimate on a new HVAC system.