What a Flame Sensor Is and Why It Matters

February 26, 2017

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 may feel like it’s always something else.

This time it’s your heat exchanger, next time it’s your control valve. 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 hot surface ignitor or a spark will actually ignite the gas. Once the gas is ignited, the flame sensor produces a current of electricity. The electricity is calculated in micro amps. If the furnace’s control board does not read the correct level of micro amps, the furnace will quit giving the system fuel to prevent an explosion.

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

The way to diagnose if a dirty 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 guilty party, the furnace expert will clean the sensor with steel wool. If dirt was the only factor, we will see a significantly higher amp reading. If the reading does not change, the technician will carry on with the heating equipment repair diagnostic process.

If you aren’t confident your heating equipment is going to make it through these last few weeks of winter, give A-PLUS 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 heating system.

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