What a Flame Sensor Is and Why It Matters

Receiving your routine furnace maintenance helps keep your furnace operating up to 30% more efficient and helps extend the life of your system. But things may still stop working, and when they do, you might feel like it’s always something else. 

This time it’s your motor, 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 a crucial safety feature on your gas furnace. 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 creates a current of electricity. The current is calculated in micro amps. If the furnace’s control board fails to read the proper level of micro amps, the furnace will quit giving the system fuel to stop an explosion. 

Over time, if the flame sensor is not cleaned properly, oxidation or carbon buildup can interfere with the flame sensor’s ability to work properly, which can end up causing the heating system to malfunction. 

The way to determine 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 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 shows no change, the technician will proceed with the heating equipment repair diagnostic process. 

If you aren’t confident your heating equipment is going to make it through these last few weeks of winter, give Service Experts Heating, Air Conditioning & Plumbing 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.