BVS Home Experts

Why Does My Furnace Make a Knocking Sound?

Are you having problems with your furnace? Katy, TX, residents can call BVS today at (281) 609-3650

As homeowners, it’s only natural to sound the alarm when we hear a strange furnace noise. Many homeowners ask, “Why does my furnace make a knocking sound?” Besides knocking, other loud noises might include clanking, rattling, or banging. 

In most cases, an appliance making loud noises indicates an issue, like a broken part. Sometimes, a furnace making a loud knocking sound isn’t an issue. 

However, you should still have HVAC technicians inspect your furnace if you hear a strange knocking sound. Doing so can rule out any issues and give you peace of mind. We’ll explore why your furnace makes sounds and why to call experts for your furnace installation in Katy, TX

Common Reasons Why Your Furnace Is Knocking

Let’s explore some of the most common answers to the question, “Why does my furnace make a knocking sound?”

Expansion and Contraction 

Do you only hear the knocking noise when you start your furnace or shortly after it stops blowing out hot air? If so, then expansion and contraction are probably the culprits. 

Expansion and contraction occur when your metal ducts, pipes, vents, and other components make noises while they heat up or cool down. While hearing these parts clang and bang together can be alarming, it usually doesn’t indicate you have an issue. 

Issues with Your Blower Fan 

Something might be stuck inside if the noise comes from your furnace’s blower fan. Objects trapped inside your blower fan can range from paper, garbage, tin foil, or even small rodents or birds. 

For DIY enthusiasts, you can clean your blower fan yourself to see if that resolves the issue. However, you can also have HVAC professionals tackle the job. If cleaning your blower fan doesn’t resolve the issue, you may need to replace or repair it. 

You Have a Dirty Blower Wheel 

A dirty blower wheel can also trigger a knocking sound from your furnace. Besides a dirty blower wheel making the job harder for your furnace, the blower itself can become unbalanced. An unbalanced blower wheel can explode if you don’t resolve the issue. 

An unbalanced or dirty blower wheel means one of two things: 

  1. You haven’t changed your furnace filter in a long time
  2. There was never a furnace filter

When there’s no furnace filter, or you haven’t replaced it in a long time, debris like dirt, smoke, pet dander, etc., will begin clogging your blower wheel. These nasty substances make your blower wheel unbalanced, creating loud noises until the wheel breaks down. 

Homeowners can avoid this issue simply by regularly replacing their furnace filters. Homeowners should aim to replace their filters every three months. However, the rate you should replace your filter depends upon these factors: 

  • How many people are in your home 
  • The size of your home 
  • If anyone in your family smokes or has breathing issues (like allergies or asthma) 
  • If you have any pets 
  • How much you use your furnace
  • Your region’s overall climate

Failing to replace your furnace filter can reduce indoor air quality and even promote mold growth. A dirty filter and blower wheel also force your furnace to work harder. When your furnace works harder, you can expect more wear and tear and higher energy bills. 

You Have a Faulty Inducer Fan Motor 

Maybe instead of asking, “Why does my furnace make a knocking sound?” they ask about squeaking noises. If your furnace is creating squeaking sounds, you may need to replace or repair your inducer fan motor. 

Your Furnace Has a Damaged Belt 

Your furnace may have other damaged parts, like bad bearings or a damaged or cracked belt. A furnace with a broken belt will make a similar sound as a car with a broken belt. 

To some, this sound resembles a knocking, while other homeowners hear it as a screeching or squealing sound. An HVAC technician can inspect your furnace. After inspection, they can determine if you have bad bearings or a worn-out belt. 

Sometimes lubrication can fix the issue, but you’ll need to replace your belt or bearings other times. 

Problems with Your Gas Burners 

Dirty burners or gas explosions can also trigger a loud knocking or banging sound. Gas burners not properly working cause gas to build up in your combustion chambers. This problem can create excessive gas pressure or a clog. 

If you believe the problem is coming from your gas burners, don’t try to fix the issue yourself. Trying to handle the situation yourself by taking apart your burners or heat exchanger can cause a gas leak. Instead, get your family outside and call an HVAC technician. 

What Can You Do About a Furnace Making Noise? 

Whether your furnace is knocking, banging, clanking, whistling, etc., it’s best to act as if something’s wrong with your furnace and call an HVAC repair company. You should never try to repair your furnace yourself for the following reasons: 

  • You can get hurt
  • You can make the problem worse
  • You may not have the right equipment 
  • You can void your furnace’s warranty 

However, experts recommend you don’t wait until your furnace starts knocking. Instead, having the right team routinely inspect your furnace is better. 

Will I Need to Replace My Furnace? 

Whether you’ll need to replace your furnace after it starts knocking depends. If you catch the problem early enough, you may only need minor repairs. However, severe damage may require a replacement. 

Another factor to keep in mind is how old your furnace is. The average furnace’s lifespan is between 15 to 20 years. If your furnace is reaching this age, it might be cheaper to replace it. 

Let Our Team Inspect Your Furnace Today 

When asking, “Why does my furnace make a knocking sound?” it’s better to let our HVAC team take a look. 

Katy, TX, residents should call BVS today at (281) 609-3650 to explore furnace safety tips and other essential information! 

Author Bio:

Ronald Via

Ronald is one of the key contributors to BVS Home Experts, a family-owned and operated full-service air conditioning and heating company serving the Katy and West Houston areas. With a deep understanding of air conditioning and heating concerns, Ronald brings a wealth of knowledge to our readers.

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