What a Flame Sensor Is and Why It Matters

Scheduling your routine furnace maintenance helps keep your furnace running up to 30% more efficient and helps extend the life of the equipment. But things can still stop working, and when they do, you might feel like you’re always hearing about something else.

This time it’s your motor, 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 a critical safety component on your gas furnace. During the ignition sequence, your gas furnace goes through a process where either a spark or a hot surface igniter actually ignites the gas. When the gas is ignited, the flame sensor produces a current of electricity. The electricity is measured in micro amps. If the furnace’s control board fails to read the right level of micro amps, the furnace will quit giving the system fuel to avoid an explosion.

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

The way to determine if an unclean flame sensor is causing a furnace malfunction is to take a micro amp draw reading, which a professional furnace technician can supply you. If a dirty flame sensor is the guilty party, the technician will clean the sensor with steel wool. If dirt was the sole factor, we will see a significantly higher amp reading. If the reading doesn’t change, the technician will carry on with the heating equipment repair diagnostic process.

If you aren’t sure your heating equipment is going to make it through these last few weeks of winter, give A-PLUS Service Experts a call and we’ll come out and give you a full furnace maintenance or a complimentary in-home estimate on a new heating system.

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