What a Flame Sensor Is and Why It Matters

February 26, 2017

Receiving your routine furnace maintenance helps keep your furnace operating 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 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 crucial safety element on your gas heating system. During the ignition cycle, your gas furnace goes through a process where a spark or a hot surface ignitor will ignite the gas. As the gas is ignited, the flame sensor creates a current of electricity. The electricity is quantified in micro amps. If the furnace’s control board fails to read the right 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 hinder the flame sensor’s ability to function properly, which can end up causing the heating system to malfunction.

The way to establish if a dirty flame sensor is causing a furnace malfunction is to take a micro amp draw reading, which an expert heating technician can provide you. If a dirty flame sensor is the guilty party, the furnace expert will clean the sensor with steel wool. If dirt was the sole factor, we will see a notably higher amp reading. If the reading does not change, the technician will continue with the furnace 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 give you a full furnace maintenance or a complimentary in-home estimate on a new heating system.

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