What a Flame Sensor Is and Why It Matters

February 26, 2017

Scheduling your routine furnace maintenance helps keep your furnace working up to 30 percent more efficient and helps extend the life of the equipment. But things can still malfunction, and when they do, you may feel like there is always something else.

This time it’s your blower, next time it’s your control valve. Now you need to replace your flame sensor.

What is a flame sensor, anyway?

A flame sensor is an important safety element on your gas heating equipment. During the ignition cycle, your gas furnace goes through a process where either a hot surface ignitor or a spark will actually ignite the gas. As the gas is ignited, the flame sensor generates a current of electricity. The current is calculated in micro amps. If the furnace’s control board does not read the right 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 appropriately, oxidation or carbon buildup can impede the flame sensor’s ability to operate properly, which can result in a malfunction of the furnace.

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 heating technician can supply you. If a dirty flame sensor is the culprit, the technician will clean the sensor with steel wool. If dirt was the single factor, we will see a significantly higher amp reading. If the reading shows no change, the technician will proceed with the heating equipment repair diagnostic process.

If you aren’t confident your furnace 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 provide you with a full furnace maintenance or a complimentary in-home estimate on a new HVAC system.

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