What a Flame Sensor Is and Why It Matters

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

This time it’s your heat exchanger, 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 an important safety feature on your gas heating equipment. During the ignition cycle, your gas furnace undergoes a process where a spark or a hot surface ignitor will actually ignite the gas. Once the gas is ignited, the flame sensor produces a current of electricity. This is measured in micro amps. If the furnace’s control board fails to read the proper level of micro amps, the furnace will quit giving the system fuel to stop an explosion.

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

The way to diagnose if a soiled flame sensor is the reason for a furnace malfunction is to take a micro amp draw reading, which a professional furnace technician can give you. If a dirty flame sensor is the guilty party, the furnace expert will clean the sensor with steel wool. If dirt was the single factor, we will see a significantly higher amp reading. If the reading doesn’t change, the technician will continue with the heating equipment repair diagnostic process.

If you aren’t sure your heating system is going to survivie 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 complimentary in-home estimate on a new heating system.

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