What Is that Noise? Common Furnace Noises and Their Meaning

checking up on your furnace

You might be settling for a good, toasty sleep when all of a sudden, you hear a racket from your furnace. The noises seem to be coming from inside the unit, but how can you shut it off when you need it for a cozy bedtime?

Before you head back to your room and put a pillow over your ears, furnace noises are a sign of broken parts that need to be serviced. Note that the first thing you should do is to turn off the furnace as soon as you hear these unusual sounds. If possible, call your furnace tune-up specialist in Salt Lake City. Here are everyday furnace noises and what they mean:

Scraping

A scraping sound, like a piece of metal is hitting another piece, usually means a broken blower wheel, but it can also mean your furnace’s motor mount is busted. If you suspect some part is loose inside the unit, you’re partially right. This happens because the blower wheel has come loose and is hitting the housing of the blower, or if it’s the motor mount, the blower wheel instead “drops” against the housing, making a clattering sound. Using your furnace, in either case, will damage both of them to the point that realignment won’t be possible and you have to buy replacement parts, so if you hear this kind of noise, shut your furnace off immediately.

Dull Thumping

Do you remember what an old dryer sounds like when your clothes aren’t appropriately loaded? When your furnace sounds like that, it means a problem—again—with the blower wheel or the motor mount. These components might be out of balance, which, if left unattended, can soon graduate to a more concerning sound: scraping. Other sources of this sound include external materials that have been caught in the return air duct, like a piece of clothing. To be sure, turn your furnace off and call your HVAC technician.

Rumbling or Booming

No, you’re certainly not hearing thunder in there. Rumbling or booming sounds indicate problems with your burner, usually a dirty one. The way it works is that a dirty burner can delay your ignition, which means the gas will instead accumulate in the furnace. A single spark will finally be able to light all that built-up gas, causing a small “explosion” to happen. This is what you hear when you hear a booming or rumbling sound.

Explosions in any home appliance are never good. It’s the height of prudence to call your HVAC technician when you hear this noise. Fortunately, dirty burners can be cleaned, but if you’ve heard this noise too long and decided to neglect it, your burners need replacement.

Humming

checking your furnace

A loud humming sound when the furnace is on means you have a bad transformer, although some sources include a struggling fan or a bad capacitor. While most transformers make a humming sound because of the electricity, a furnace’s is whisper-quiet. A loud one is a cause for concern and can lead to shorting the device out or causing a fire. It’s not as urgent as the others on this list, so if you still have heat and the furnace is working, call your HVAC technician to drop by the next morning and see what can be done.

You can troubleshoot your furnace on your own, but they’re a band-aid solution at best. A professional with the right training can fix your problems permanently and give you peace of mind.