What a Flame Sensor Is and Why It Matters

Scheduling your annual furnace maintenance helps keep your heating system operating up to 30% more efficient and helps extend the life of the equipment. But things could still go wrong, and when they do, you may feel like you’re always hearing about 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 cycle, your gas furnace goes through a process where either a spark or a hot surface igniter actually ignites the gas. When the gas is ignited, the flame sensor creates a current of electricity. This is measured in micro amps. If the furnace’s control board does not read the correct level of micro amps, the furnace will stop giving the system fuel to prevent an explosion. 

Over time, if the flame sensor is not cleaned properly, oxidation or carbon buildup can interfere with the flame sensor’s ability to function properly, which can cause the furnace to malfunction. 

The way to determine if a dirty flame sensor is to blame for a furnace malfunction is to take a micro amp draw reading, which an expert furnace technician can provide you. If a dirty flame sensor is the culprit, the technician will clean the sensor with steel wool. If dirt was the only factor, we will see a much higher amp reading. If the reading does not change, the technician will proceed 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 Service Experts Heating, Air Conditioning & Plumbing a call and we’ll come out and provide you with a full furnace maintenance or a free in-home estimate on a new heating system. 

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