Why Is Your Furnace Making a Clicking Noise?

Hearing a clicking noise coming from your furnace can be quite disconcerting. This noise usually indicates that there is either some issue preventing the furnace from turning on or keeping it from working properly. This can happen for a variety of different reasons, and here are some of the most common problems that can cause a furnace to make clicking sounds and how to overcome them.

Malfunctioning Electric Igniter

Unless your furnace is quite old, it most likely uses some type of electronic ignition. Many older furnaces use a standing pilot light, but these have mostly been phased out, as the constant flame wastes quite a bit of energy. Most newer gas furnaces use an intermittent pilot, also referred to as “direct-spark ignition.”

You can think about this as similar to the spark igniter found on most gas barbecue grills. Whenever the furnace needs to start, it uses electricity to create a spark that ignites the gas flowing into the unit. Over time, this electronic igniter can start to fail and not always create a spark. The same problem can also occur if the igniter’s wiring or electrical connections are loose. In either gas, the igniter will continually produce an audible clicking noise every time it tries to spark, and the noise will continue for at least a few seconds until the furnace ignites or the gas valve closes.

Dirty Flame Sensor

All gas furnaces with an electric igniter have a flame sensor that detects whether the gas inside the unit is lit. The flame sensor both controls the igniter and opens and closes the gas valve. When everything is working properly, the flame sensor opens the valve to allow gas to flow into the furnace. This signals the igniter to create a spark. If the gas ignites but the sensor can’t detect the flame, the igniter will continue to try to create a spark for at least a few seconds, resulting in it making multiple clicking noises. If the sensor still doesn’t detect the flame, it will then automatically close the valve so that no more gas flows into the furnace and the furnace will then shut off.

The sensor works by detecting the heat from the flames inside the furnace. If you don’t have your furnace maintained and cleaned regularly, the flame sensor will often become covered in a layer of dirt and grime. This grime can essentially act as an insulator and prevent the sensor from detecting the heat, thus leading to clicking sounds coming from the igniter and the furnace shutting down within a few seconds of starting. A dirty flame sensor is one of the easiest issues to prevent, as all you need to do is make sure to have your heating system professionally maintained every year.

Gas Supply Issues

You will also hear a clicking noise coming from the furnace if the gas supply is ever interrupted for any reason. This can happen if the gas line is kinked or clogged, the gas valve isn’t fully open, or simply because your main gas supply cuts out for some reason. If there is no gas flowing to the furnace, the igniter will start making a clicking sound whenever the furnace tries to start, and this sound will typically continue until you shut your heating off at the thermostat.

This issue is usually fairly easy to detect as your furnace won’t ever turn on. You can also listen when it tries to start to see if you can hear any gas flowing. If you can’t hear the gas flowing, you should check to see if your other gas appliances like a water heater or fireplace are working. If these other units are working, you’ll need to have your furnace and its gas supply inspected to determine what is preventing the gas from flowing. If none of your gas appliances are working, you will need to call your gas company to see what the issue is.

Faulty Start Capacitor

This issue is related to the blower fan and not the furnace itself, but it can still produce loud clicking noises when your heating system starts. It is also easy to detect as it will prevent your fan from running. All blowers have something known as a start capacitor that helps to supply the huge surge of energy needed for the blower motor to start. The capacitor works by storing a strong electrical charge that it releases whenever the fan needs to start.

If the capacitor starts to wear out, it will usually produce a clicking sound and may prevent the fan from running. This same issue is also why air conditioners sometimes make a clicking noise as these units have their own capacitor that serves the same function to help the compressor motor and AC fan motor start. Luckily, replacing a failed start capacitor is one of the easier fixes, but it is still something you will need a certified technician to do for you.

Worn-Out Fan Bearings

Most newer blower fans have a direct-drive motor that uses bearings to help it a spin. These bearings can often wear out and either prevent the fan from running at all or cause it to not work properly. If the bearings are fully worn out, the fan will often make a loud humming noise whenever it attempts to start. When the bearings first start to fail, they will often result in the fan making clicking, squealing, or grinding noises.

In either case, the only option is to have a technician replace the fan bearings. If you don’t have the bearings replaced, it could cause the blower motor to overheat and burn out, which means you would then need to replace the entire blower motor.

Broken Fan Blades

This last issue is fairly rare, but it can occur if you don’t have your HVAC system maintained regularly. Although your air filter should trap most debris, some dirt and dust will still always get inside your HVAC system. This dust can collect on the fan blades and throw everything off balance, which can sometimes result in the blades grinding against the fan housing and potentially breaking off. The loose fan blade will then often make a loud clicking sound whenever the fan is running, and this is similar to the sound you’d hear if one of the fan blades in your laptop is broken.

Tucson’s HVAC Experts

If your furnace is making clicking sounds or other unusual noises, you can count on the team at Fusion Plumbing & Air to quickly get to the bottom of the issue to ensure that your heating system again works properly. We inspect, maintain, and repair all types of furnaces from any manufacturer, and we also carry an extensive selection of new units should you need to have your furnace replaced.

We install, repair, and maintain air conditioning systems for both residential and commercial customers as well. If you need any plumbing service, we can also help with that. Our team specializes in drain cleaning, gas lines, sewer lines, water heaters, water filtration systems, and a range of other plumbing services. If you need any type of heating, cooling, or plumbing service in Tucson or the surrounding areas, give us a call today.

Fusion Plumbing & Air

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