What a Flame Sensor Is and Why It Matters

Scheduling your seasonal furnace maintenance helps keep your heating equipment running up to 30 percent more efficient and helps extend the life of your furnace. But things can still go wrong, and when they do, you might feel like it’s always something else.

This time it’s your motor, next time it’s your pressure switch. Now you need to replace your flame sensor.

What is a flame sensor, anyway?

A flame sensor is an important safety feature on your gas heating equipment. During the ignition sequence, your gas furnace goes through a process where either a hot surface ignitor or a spark will ignite the gas. When the gas is ignited, the flame sensor generates a current of electricity. The current is measured in micro amps. If the furnace’s control board doesn’t 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 appropriately, oxidation or carbon buildup can interfere with the flame sensor’s ability to operate properly, which can cause the furnace to malfunction.

The way to diagnose if a soiled flame sensor is to blame for a furnace malfunction is to take a micro amp draw reading, which an expert furnace technician can supply you. If a dirty flame sensor is the reason, 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 proceed 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 give you a full furnace maintenance or a free in-home estimate on a new furnace.

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