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Banging, Grinding, Whining: 3 Furnace Noises You Shouldn’t Ignore

Banging, Grinding, Whining: 3 Furnace Noises You Shouldn’t Ignore

An old furnace can make all sorts of loud noises when you turn it on. While many aren’t any cause for concern, there are three furnace noises you should never ignore. If your furnace is creating a banging, grinding, or whining noise, this is a sign of an issue that needs to be addressed. We’ll explore what is causing these noises and what should be done to stop them.

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1. Banging Noise When the Furnace Kicks On

Common causes of banging noises include: We have created an outline of various issues that may cause your furnace to produce a loud banging noise.

Dirty Furnace Burners

Does it take several seconds to a minute before the furnace comes on after you call for heat? This is a delayed ignition caused by dirty furnace burners. The dirt keeps the burners from igniting the gas, so the gas builds up.

Once the gas ignites the system will make a loud banging noise when it is turned on. Basically, it’s a mini-explosion in the furnace. Don’t ignore this noise. If you hear a banging or knocking noise, the source of the issue may be small explosions that can crack the heat exchanger, which is expensive to repair.

Expanding Air Ducts

If you hear this noise several feet from the furnace, then it’s probably the ducts expanding as the furnace blower turns on. This excessive expanding can be due to:

  • Undersized ducts (talk to a contractor to see if this is the case)
  • Closed vents (open more of your vents)
  • Flimsy ducts (brace the ducts)
  • A dirty air filter (change their air filter if it’s dirty)

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2. Loud Grinding (Metal Rubbing Metal) Noise

The cause of this noise is usually a problem with the squirrel cage blower wheel in the furnace. If you hear this noise, turn off your furnace immediately to prevent any further damage to the system and call a professional to perform a furnace repair project.

A few blower wheel problems include:

  • Blower wheel is loose from the motor wheel. Get a professional to tighten the wheel
  • The blower wheel is broken and needs replacing
  • The motor mount broke, causing the whole blower assembly to drop and hit the housing

3. Whining Noise

This loud noise in your furnace isn’t as serious as the other two, but it needs addressing all the same. This noise is usually caused by:

  • A loose, slipping, or fraying blower belt. This should be adjusted by a technician or replaced if it’s fraying.
  • Shaft bearings that need oil. Add lightweight oil to the lubrication port at each end of the shaft.
  • A malfunctioning blower motor. This needs to be fixed or replaced by a professional.

Banging, Grinding, Whining: 3 Furnace Noises You Shouldn’t Ignore

Furnace Repair & Installation Services

If your furnace is making a grinding, whining, or knocking noise, give our professionals a call at (508) 301-1767 to book an appointment. Our team of technicians have experience with all furnace make and models. Our professionals provide dependable heating and HVAC repair services in Marlborough, MA and other areas. When you need help with a furnace replacement or furnace repair project in your house, contact our team to receive help. If your furnace is making any of the noises outlined above, our team is available to inspect your system.