What a Flame Sensor Is and Why It Matters

February 26, 2017

Scheduling your seasonal furnace maintenance helps keep your furnace operating up to 30 percent more efficient and helps extend the life of the equipment. But things could still malfunction, and when they do, you may feel like it’s always something else.

This time it’s your blower, next time it’s your pressure switch. Now you have to have your flame sensor replaced.

What is a flame sensor, anyway?

A flame sensor is a critical safety feature on your gas heating equipment. During the ignition sequence, your gas furnace undergoes a process where either a hot surface ignitor or a spark will actually ignite the gas. Once the gas is ignited, the flame sensor creates a current of electricity. The current is quantified 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 avoid an explosion.

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

The way to determine if a dirty flame sensor is the reason 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 culprit, 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 does not change, the technician will continue with the heating system repair diagnostic process.

If you aren’t certain your furnace is going to survivie these last few weeks of winter, give Fras-Air/General 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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