4 Lesser Known Furnace Components You Should Know About

When it comes to what components make up your furnace, many people already know about how the blower motor and heat exchanger work. However, there are other components that may not be as obvious without further research. Here is what you need to know about some of those additional components that help the furnace do its job, which can help you diagnose the need for a potential repair.


There are different types of ignitors that are used to start up your furnace, with two of the most common ones being spark ignitors and hot surface ignitors. A hot surface ignitor works by heating up to a specific temperature with electricity, which is what causes the part to glow a bright orange color. Gas is then released and ignited by the hot surface ignitor to start the furnace. A spark ignitor works by creating a spark that lights the gas. Both types of ignitors get th­e job done, but just do it in different ways.

Flame Sensor

As the name implies, a flame sensor has the job of sensing if there is an active flame in the furnace. It is essentially a safety switch, which shuts off the gas if the furnace ignitor fails. If there is no flame, the gas is not combusting and can potentially leak into your home. The flame sensor can tell that there is no flame and shut down the furnace.

A common problem with a flame sensor is that it can become dirty over time. If this happens, the flame sensor will not sense that a flame is active even if there is one. This can cause the furnace to shut down even though it is working properly. Cleaning the flame sensor is simple to do and can get your furnace up and running again.

Control Board

Your furnace's control board is basically the brains of the appliance. It's a circuit board that has the job of sending power to all of the components of the furnace. This is a part that should be inspected if a component of your furnace that requires electricity is not working, as the control board may have a problem sending electricity to that part.


The job of the capacitor is to ensure that the blower motor can run. Rather than have electricity flow directly to the blower motor, the capacitor stores and steadily releases it to the blower motor. This keeps the blower motor moving at a steady and consistent speed. A bad capacitor can cause the blower motor to make a loud sound, stop working, or cause a clicking noise prior to it failing completely.

Reach out to a heating service to learn more.