What a Flame Sensor Is and Why It Matters

Scheduling your annual furnace maintenance helps keep your heating system working up to 30% more efficient and helps extend the life of the equipment. But things may 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 need to replace your flame sensor. 

What is a flame sensor, anyway? 

A flame sensor is an important safety element on your gas heating system. During the ignition sequence, your gas furnace undergoes a process where a spark or a hot surface ignitor actually ignites 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 does not read the correct level of micro amps, the furnace will stop giving the system fuel to avoid an explosion. 

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

The way to determine if a dirty flame sensor is to blame for a furnace malfunction is to take a micro amp draw reading, which a professional furnace technician can provide you. If a dirty flame sensor is the culprit, the technician will clean the sensor with steel wool. If dirt was the only factor, we will see a much higher amp reading. If the reading doesn’t change, the technician will continue with the heating system repair diagnostic process. 

If you aren’t certain your heating system is going to survivie these last few weeks of winter, give A-Plus a call and we’ll come out and provide you with a full furnace maintenance or a free in-home estimate on a new heating system. 

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