It’s common for older furnaces to make a lot of noise. Many sounds, such as quiet popping or humming, are normal, but other sounds, such as loud thumping or squealing, are signs that something is wrong. If your furnace is making unusual sounds, get it inspected. A variety of issues can cause funny noises, and timely treatment can save you hundreds, if not thousands, of dollars.
An out-of-balance motor can cause loud thumping sounds. While it’s normal for your furnace to quietly thump when it’s turning off, an out-of-balance motor will cause loud, consistent thumps while the unit is running. Immediate repair is required because an unbalanced motor can do serious damage to your furnace. It’s a good idea to leave your unit off until a technician can work on it.
Damaged Belts or Bad Bearings
If you hear a continuous knocking sound that occurs when your HVAC unit is running, it likely means the system has a damaged belt or bad bearings. It’s important to have them replaced before they cause extensive damage.
Don’t worry about knocking that only happens when the system is turning on and off. This is usually caused by expansion and contraction of the sheet metal in the ductwork and is rarely cause for concern.
A Worn Out Belt, Motor, or Fan
Worn out belts, motors, and fans are common causes of loud squealing sounds. Over time, these components wear out and require replacement. However, squealing sounds can come from a variety of sources, and almost all of them require an HVAC technician’s attention.
Another common cause of squealing is blower housing and motor wheel misalignment. If not properly aligned, the two components will scrape against each other, creating friction that’ll cause a shrill squealing noise.
Out-of-Balance Blower Wheels
If you hear constant rattling sounds from your furnace, the blower wheels are probably out of balance. Blower wheels must remain in balance to work efficiently, and they usually come with balancing weights and clips attached to them to maintain balance. If any of the attached clips or weights slip out of place or detach, you’ll hear rattling sounds. It’s also common for dirt to build up under the blower wheels and act as additional weight, throwing the wheels out of balance.
While you can’t prevent every problem that can occur with your furnace, having your HVAC system serviced on a regular basis can prevent many common issues. For instance, having the unit regularly maintained is the best way to keep dirt from building up inside it and throwing it out of balance. Investing in a maintenance agreement allows HVAC technicians to replace parts before they wear out, saving you a service call.
HVAC units make lots of noises, and recognizing which ones are normal and which ones aren’t is key. To minimize worrisome sounds, such as loud squealing, knocking, and rattling, have your unit serviced on a consistent basis. Regular maintenance can prevent many expensive problems while extending the life of your unit by years.