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.
Out-of-Balance Motor
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
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,
HVAC units make lots of noises, and recognizing
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