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Furnace Making Growling Noise? 4 Common Causes (+ Fixes)

A loud, growling sound coming from your furnace is pretty alarming. Usually, it’s a smaller issue causing the noise, but complications can develop if you don’t address it on time. Understanding why the growling sound may occur is the first step to diagnosing and fixing the problem. 

Your furnace is making a growling noise because of dirty burners, a faulty pilot light, dirty or failing flame sensor, or problems with the combustion chamber. Fixes include cleaning the burners, reigniting the pilot light, replacing or cleaning the flame sensor, and checking the combustion chamber.

This article is a guideline on why your furnace is making a growling noise when turned on. You’ll also learn how to fix each potential problem to eliminate the unsettling noise. 

The Burners Are Dirty

There are many instances where seemingly insignificant problems cause the loudest noises. This is the case here — burners that are too dirty to work effectively. After all, millions of microscopic particles run through the furnace each day. As the burner runs, substances such as carbon monoxide accumulate on the burner’s surface. 

While many people associate a sparking sound with a dirty burner, there are cases where this may be the source of a furnace making a growling noise. As soot keeps accumulating, you’ll notice the flames getting weaker. When this happens, the furnace won’t heat your home effectively. You’ll also notice that the room temperature will never reach the one you set on the thermostat.

How To Fix

The easiest solution for this problem is to clean the dirty burners. Burners are relatively small, so you should practice caution while working on them. You also need the appropriate tools to clean the burners to remove as much debris as possible. Here’s how to do it:

  1. Shut the furnace off.
  2. Open the main furnace panel.
  3. Locate the burners. They’re close to the combustion chamber and ignitor.
  4. Remove the burner from its location. You need to use tools to do this. 
  5. Take a look at the burner and see if there’s a lot of debris on the surface. If that’s the case, clean it thoroughly. Use a toothbrush to remove debris inside thetinyl holes you see in the burner. 

Make sure to look for damage too. If you find cracks or other signs of damage, consider getting a replacement for the burner. 

Here’s a video to help you with the process:

The Pilot Light Isn’t Properly Configured

Many people still use older furnaces with pilot lights. The pilot light produces a tiny flame that ignites the burners.

The pilot light needs to be appropriately adjusted to work. Note that this issue only applies to older furnaces. Newer models use an electric ignitor instead of a pilot light.

If there’s a problem with the pilot light, it can result in a growling sound. Sometimes, it’s just a dirty pilot light; other times, the component is faulty and needs to be replaced.

How To Fix

The first step is to determine whether there is a problem with the pilot light or it’s just dirty. You’ll again have to open your furnace to fix the pilot light. Ensure your furnace uses a pilot light and not an ignitor by referring to the owner’s manual to avoid wasting time.

Without any further ado, here’s how to fix the pilot light:

  1. Turn off your furnace.
  2. Open the main compartment.
  3. Locate the pilot light. You’ll notice the pilot light is a tiny device that sits close to the burner. 
  4. See if there’s debris on the pilot light. If there is, thoroughly clean the component with a steel wire or brush. 
  5. If you don’t see anything blocking the pilot light, it might be faulty. See if you can find burn marks on the device or a loose connection. 

The fix depends on the fault you identify, but a replacement pilot light is almost always the best and safest option.

The video below will provide you with the instructions on replacing the pilot light: 

The Flame Sensor Is Dirty or Faulty

Another component you want to look at is the flame sensor. If the flame sensor is dirty, it can’t do its job — detecting a flame and regulating gas supply toward the burners. 

If the flame sensor runs into problems, the gas supply can become faulty. This can also lead to weird growling noises coming from the furnace. This happens when the gas supply is too low for the ignitor to work effectively, causing a build-up of gases in the chamber where the burner is located. 

How To Fix

The sensor is located in the combustion chamber. 

Removing the flame sensor allows you to inspect it. Use fine-grit sandpaper to remove residue. While at it, look for cracks or other signs of damage. If there are no cracks, reinstall the sensor after cleaning. If you notice cracks, consider replacing it.

This video gives you a step-by-step overview of how you can clean the flame sensor: 

There Are Problems With the Combustion Chamber

Depending on the type of furnace you have, the problem causing the growling noise may lie in the combustion chamber itself. For example, leftover oil in the chamber after a heating cycle can cause a growling or rumbling noise. This won’t happen with all types of furnaces, but it’s still a good idea to investigate. 

How To Fix

You need to inspect the combustion chamber to determine if this is causing the growling noise. You must know how to open the component without causing any damage. If you see any damage in the combustion chamber, it needs replacing. If oil is left after a heating cycle, you need to determine why this happened and address the source of the problem accordingly. 

Summary

When a furnace makes a growling sound, it may indicate a problem that’s easy to fix. Sometimes, something as simple as cleaning the burners is enough. In other instances, the problem may have a more serious underlying cause.

Author

  • Jake Alexander

    Jake is a freelance writer from Pennsylvania who enjoys writing about science and sports. When he's not writing for Temperature Master, he can be found watching the NFL or playing basketball with his friends.

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