What a Flame Sensor Is and Why It Matters

February 26, 2017

Receiving your seasonal furnace maintenance helps keep your heating equipment operating up to 30 percent more efficient and helps extend the life of the equipment. But things could 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 valve. Now your find out the flame sensor has to be replaced.

By the way – what is a flame sensor?

A flame sensor is a crucial safety element on your gas furnace. During the ignition sequence, your gas furnace undergoes a process where either a spark or a hot surface igniter will actually ignite the gas. Once the gas is ignited, the flame sensor creates a current of electricity. The electricity is calculated in micro amps. If the furnace’s control board does not read the proper level of micro amps, the furnace will no longer give 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 result in a malfunction of the furnace.

The way to establish if an unclean flame sensor is causing 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 reason, the furnace expert will clean the sensor with steel wool. If dirt was the sole factor, we will see a significantly higher amp reading. If the reading does not change, the technician will proceed with the furnace repair diagnostic process.

If you aren’t certain your heating equipment is going to survivie 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 free in-home estimate on a new HVAC system.

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