What a Flame Sensor Is and Why It Matters

Setting up your seasonal furnace maintenance helps keep your furnace operating up to 30 percent more efficient and helps extend the life of your furnace. But things could still malfunction, 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 a crucial safety component on your gas furnace. During the ignition sequence, your gas furnace enters a process where either a spark or a hot surface igniter will ignite the gas. When the gas is ignited, the flame sensor generates a current of electricity. The current is measured in micro amps. If the furnace’s control board fails to read the proper level of micro amps, the furnace will stop giving the system fuel to prevent an explosion. 

Over time, if the flame sensor is not cleaned appropriately, oxidation or carbon buildup can restrict the flame sensor’s ability to work properly, which can result in a malfunction of the furnace. 

The way to diagnose if an unclean flame sensor is causing a furnace malfunction is to take a micro amp draw reading, which an expert furnace 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 doesn’t change, the technician will proceed with the furnace repair diagnostic process. 

If you aren’t confident your heating system is going to survivie these last few weeks of winter, give Stevenson Service Experts a call and we’ll come out and give you a full furnace maintenance or a complimentary in-home estimate on a new HVAC system. 

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