What a Flame Sensor Is and Why It Matters

February 26, 2017

Scheduling your annual furnace maintenance helps keep your heating equipment working up to 30% more efficient and helps extend the life of your furnace. But things could still stop working, 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 your find out the flame sensor has to be replaced.

By the way – what is a flame sensor?

A flame sensor is a critical safety feature on your gas furnace. During the ignition pattern, your gas furnace goes through a process where either a hot surface ignitor or a spark actually ignites the gas. As the gas is ignited, the flame sensor creates a current of electricity. The current is quantified in micro amps. If the furnace’s control board does not read the right level of micro amps, the furnace will quit giving the system fuel to prevent an explosion.

Over time, if the flame sensor is not adequately cleaned, 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 dirty flame sensor is causing a furnace malfunction is to take a micro amp draw reading, which an expert heating technician can give you. If a dirty flame sensor is the offender, the technician will clean the sensor with steel wool. If dirt was the single factor, we will see a significantly higher amp reading. If the reading does not change, the technician will carry on with the furnace repair diagnostic process.

If you aren’t certain your heating system is going to make it through these last few weeks of winter, give Eveready 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 furnace.

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