Tips For Troubleshooting A Furnace Flame Sensor

Are you in a situation where your heat is not working and you're not quite sure what to do? This problem may actually be due to the flame sensor. Here are some tips for how you can troubleshoot this unique furnace problem.

Reset The Furnace Lockout

Newer furnaces have a lockout feature, where it will prevent the furnace from constantly trying to turn on and releasing gas into the home when the flame is not igniting. It may be set to just shut down the furnace for several hours if the flame sensor is triggered several times in a row. This means that you can't turn on your furnace while the lockout feature is active. You may need to turn off the power to the furnace and turn it back on to reset that furnace lockout feature. Since you can't troubleshoot a furnace in lockout mode, resetting it will make it possible to investigate the problem

Observe The Furnace Turning On

The next thing that you should do is open up your furnace and observe it turning on. There is an order of operation that happens that can help pinpoint a problem with what is not working. The first thing that will happen is the inducer motor will turn on. You will then have either one or two pressure switches close, with furnaces that have two-stage heating having two pressure switches. The igniter will then start to glow, which starts to turn that bright orange color that lets you know it is working. The gas valve will then open, the flame turns on, and your furnace starts producing heat. 

Identify A Dirty Flame Sensor

If your furnace gets to the last stage of the process of turning on, but the flame goes out after a few seconds, you likely have a dirty flame sensor. The purpose of this sensor is to verify that there is an active flame burning the fuel. If there is no flame, then it is going to shut down the furnace so that you do not have gas leaking into your home. Replacing or fixing the flame sensor is a relatively cheap fix that can resolve the problem and keep your furnace running. 

Repair The Dirty Flame Sensor

It is actually possible for you to remove the flame sensor and clean it to remove the soot that is stuck to the flame sensor. You can also replace the flame sensor with a brand new one, giving you a new part that is sure to work. The problem with cleaning a flame sensor is that if you clean it with a material that is too abrasive, it can actually make it possible for soot to easily stick to the flame sensor. 

If you suspect your flame sensor is broken, talk to a heating repair professional.