What a Flame Sensor Is and Why It Matters

February 26, 2017

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

This time it’s your blower, next time it’s your control board. Now your find out the flame sensor has to be replaced.

What is a flame sensor, anyway?

A flame sensor is an important safety feature on your gas heating equipment. During the ignition pattern, your gas furnace undergoes a process where either a spark or a hot surface igniter will actually ignite the gas. As the gas is ignited, the flame sensor generates a current of electricity. The electricity is calculated 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 impede the flame sensor’s ability to operate properly, which can cause the furnace to malfunction.

The way to establish if a dirty flame sensor is the reason for a furnace malfunction is to take a micro amp draw reading, which a professional furnace technician can provide you. If a dirty flame sensor is the offender, 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 does not change, the technician will carry on with the heating equipment repair diagnostic process.

If you aren’t certain your heating equipment is going to make it through these last few weeks of winter, give San Antonio Air Service Experts 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 heating system.

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