9 Common Furnace Noises and What They Mean

Over time, when you fire up your furnace, you know how it’s supposed to sound. So you'll likely notice if the unit starts making odd sounds. Some noises — like a couple of minor pops or clicks ahead of the warm air beginning to blow — are normal and harmless. But others could impair the equipment or even threaten your health if you neglect them. While there are many more furnace noises to consider, here are nine that warrant an immediate furnace repair.

Scraping Furnace Noise

The moment you hear a sound like metal scraping on metal, this could mean the blower wheel has come loose from the motor shaft, or the wheel or motor mount is broke. No matter the exact problem, you should shut off your furnace if you hear a scraping sound and call a professional for an critical repair.

Loud Boom at Startup

When your furnace starts up, the burners should ignite without delay and begin heating your home. A loud boom at startup probably means the burners are dirty, producing a delayed ignition. When the gas eventually does ignite, you hear this terrifying furnace noise.

A small boom each time your furnace turns on could break the heat exchanger, an expensive repair that might require you to remove and replace the entire furnace. Don't wait to act when you hear a noise like that! Switch off your furnace if you hear a loud boom at startup, and do not activate it again until it has been repaired.

Squealing or Whining Sounds

A high-pitched squealing furnace noise usually indicates poor lubrication. Shaft bearings and other moving parts require lightweight oil to operate smoothly. If these parts are dry, components grate against each other and cause unwanted wear and tear. Our recommendation is to have this issue remedied right away to prevent premature furnace failure.

Chirping Noise

The sound of a bird caught in your furnace definitely warrants investigation. If you notice chirping coming from the furnace upon the first activation of the season, it could simply mean your furnace is warming up after several months of no use. In this case, the sound should end after a few cycles.

However, if the chirping doesn’t subside, it could indicate the pulley for the blower motor is out of alignment or the mounting plate is touching the blower wheel. This isn’t automatically a safety hazard, but the only way to stop the pesky furnace noise is to have a technician conduct a repair.

Screeching Furnace

Screeching noises are clear and certain signs that the fan belt is failing. If the fraying belt cracks, it could spin inside the furnace, damaging other components and resulting in a much more expensive repair. Insulate yourself from this hassle by replacing the worn-out belt sooner rather than later.

Persistent Clicking.

Some furnaces give off a quick series of clicks when they turn on and off. This is completely normal. That said, if the noise persists longer than about one minute, this could signal an electrical issue. Don't risk your home catching fire by a faulty electrical situation; call a furnace repair professional to fix the problem promptly.

Thwapping Sounds

The blower motor should function smoothly when the furnace turns on. If you notice a thwapping sound that dramatically picks up speed as the blower gets going, this likely means something is caught in the fan, and the blades are striking it with each rotation. A simple repair should be all it takes to get rid of this annoying furnace noise and prevent damaging the blower motor.

Rattling Furnace

A few different problems can cause your furnace to rattle. It might be as simple as a loose door cover, so start there. If the rattling continues, the most plausible root cause is a declining blower motor. Treat this as a warning sign to have your furnace repaired before it breaks down completely.

Whistling or Vibrating

When your furnace has an air intake vent issue, you will often hear a whistling or humming vibration sound. If the whistling or vibrating comes from a vent, your ductwork is likely loose, allowing conditioned air to escape. These aren’t urgent matters, but if you fix it soon, you’ll spend less on your heating and cooling bills over the long haul.

Schedule Furnace Repair with Service Experts Heating & Air Conditioning

Are you uncertain whether the furnace noises you hear match these descriptions? Perhaps nothing is wrong, but if you want to be 100% sure, the easiest thing to do is to call a professional. At Service Experts Heating & Air Conditioning, we provide emergency furnace repair to get your system functioning properly as quickly as possible. Rest assured knowing that we stand behind our work with a one-year, 100% satisfaction guarantee. If you’re disappointed with our work anytime in the next 12 months, we’ll get it corrected! For more information or to arrange a furnace repair visit, please contact a Service Experts office near you.

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