When working properly, your furnace should operate with little to no sound. If you’re constantly aware that your furnace is running due to a persistent whir, rattle, or bang, you have an issue that needs to be addressed right away. Don’t let furnace noises go undiagnosed. As with most HVAC issues, these problems tend to worsen the longer they’re left to linger. Keep your Cottontown, Tennessee, home warm and cozy by calling a professional as soon as you notice these noises.

Knocking Sounds

An ongoing knocking sound can indicate many things, including worn bearings, a cracked belt, a malfunctioning gas valve, or dirty burners. These issues all require professional attention. The only knocking noise that’s not a cause for concern is one caused by the metal housing around vents and pipes. These might knock briefly as they expand or contract when the system first turns on and off. The change in temperature can cause this brief knock. If the knock is more regular, however, you should reach out to a technician for a professional diagnosis.

Rough Grinding

If your furnace makes a grinding noise, you should turn it off immediately and contact one of our technicians. This sound indicates a loose cage blower wheel. If you continue to operate the furnace, you could do permanent damage to this component. A technician must come and tighten the component for you, calibrating it properly to spin freely. If the blower wheel or motor mount is already past repair, you may need to invest in one or more replacement parts.

Thumping or Thudding

A loud, regular thump or thud that sounds continuously as your furnace is running is probably an unbalanced blower wheel or motor. You’ll hear the sound of the rotation as the wheel or motor whirls unevenly in your system. You should have the part balanced as quickly as possible to avoid further damage. If you don’t address the issue in a timely manner, you’ll likely face a total system failure, leaving you entirely without heat.

You can often avoid this type of problem by keeping up with your regular maintenance visits. During your annual tune-up, our technicians thoroughly clean, inspect, and balance key parts of your system. We can catch poor calibration of key components at this time, and we’ll adjust the blower wheel or motor before it’s so off balance that you can hear the rotation. Ideally, you will schedule your furnace maintenance at the beginning of the heating season. However, if you haven’t seen a technician in the last 12 months, you should go ahead and schedule this visit now.

Screeching and Squealing

Your furnace can make a squealing sound similar to what you hear from your car if you have a worn belt. The cause is very similar in your furnace. This sound typically means that you have a worn belt or poorly maintained bearings in your system. Adding lubrication and replacing the appropriate part will resolve the issue for you. This is another problem that you can often catch early with regular maintenance. Have the belts replaced regularly to extend the life of your system and avoid any uncomfortable downtime in the chill of winter.


This is one of the more subtle sounds you may notice from your furnace, but it’s no less concerning. This type of noise sounds a lot like a person who’s having trouble breathing. The cause is fairly similar. Your furnace might make a wheezing sound when the filter is dirty and it’s struggling to pull air through efficiently. If you hear a consistent wheezing noise when your furnace is running, your filter is the first thing you should look at. Swap it out for a fresh clean replacement and you may eliminate the noise immediately. Although you can typically go two or three months without a filter change, you should change it sooner if you have pets, children, or dust buildup.

If you’re noticing the aforementioned issues or other concerning noises from your furnace, give Bentley’s Air Conditioning a call at (615) 754-2665. We provide prompt repair services that will get your system back to a quiet hum in no time.

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