What a Flame Sensor Is and Why It Matters

February 26, 2017

Scheduling your annual furnace maintenance helps keep your furnace running up to 30 percent more efficient and helps extend the life of your furnace. But things can still stop working, 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 valve. Now you need to replace your flame sensor.

By the way – what is a flame sensor?

A flame sensor is a crucial safety component on your gas furnace. During the ignition sequence, your gas furnace undergoes a process where a spark or a hot surface ignitor will actually ignite the gas. As the gas is ignited, the flame sensor creates a current of electricity. The electricity is measured in micro amps. If the furnace’s control board does not read the proper level of micro amps, the furnace will stop giving the system fuel to avoid an explosion.

Over time, if the flame sensor is not cleaned properly, oxidation or carbon buildup can hinder the flame sensor’s ability to function properly, which can result in a malfunction of the furnace.

The way to establish 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 give you. If a dirty flame sensor is the reason, the heating 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 shows no change, the technician will carry on with the furnace repair diagnostic process.

If you aren’t certain your furnace is going to outlast these last few weeks of winter, give Service Experts Heating & Air Conditioning a call and we’ll come out and perform a full furnace maintenance or a no-charge in-home estimate on a new furnace.

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