What a Flame Sensor Is and Why It Matters

Receiving your seasonal furnace maintenance helps keep your furnace running up to thirty percent more efficient and helps extend the life of your system. But things could still go wrong, and when they do, you may feel like you’re always hearing about something else.

This time it’s your heat exchanger, next time it’s your control valve. Now you have to have your flame sensor replaced.

By the way – what is a flame sensor?

A flame sensor is an important safety component on your gas heating system. During the ignition sequence, your gas furnace enters a process where a spark or a hot surface ignitor will ignite the gas. As the gas is ignited, the flame sensor generates a current of electricity. This is quantified in micro amps. If the furnace’s control board fails to read the correct level of micro amps, the furnace will no longer give 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 end up causing the heating system to malfunction.

The way to determine 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 supply you. If a dirty flame sensor is the reason, the heating expert will clean the sensor with steel wool. If dirt was the single factor, we will see a notably higher amp reading. If the reading does not change, the technician will carry on with the heating system repair diagnostic process.

If you aren’t sure your heating system is going to outlast these last few weeks of winter, give Finch Air Conditioning & Heating a call and we’ll come out and perform a full furnace maintenance or a no-charge in-home estimate on a new HVAC system.

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