FAQ: Furnace is Noisy or Loud

A furnace that is noisy or loud may be a heating repair concern. Some noises are normal and can be expected, while others indicate an issue.

Furnace is noisy or loud – what is normal?

  • A gentle hum as the furnace operates. This is just regular operating noise from the mechanical system.
  • A click as the furnace turns on – you may hear this from your thermostat when a heating cycle begins.
  • The furnace “firing up”. You may hear the furnace starting up as it initiates a heating cycle. The noise should just be slight, not loud or disturbing.
  • A whoosh as conditioned air begins to move through room vents once the heating cycle begins.


Furnace is noisy or loud – what is a problem?

  • Metal on metal can indicate broken components, as well as inflicting further damage to the system if you continue to operate the furnace when this noise is present.
  • Squealing often indicates a worn-out fan belt or other component, requiring replacement.
  • A popping noise as the furnace warms up can indicate problems such as malfunctioning gas valves, bad bearings, or other component problems. Expanding air ducts also cause this noise, which is a sign of under-sizing or flimsy ductwork.
  • Loud banging when the furnace starts can be caused by dirty burners. Left unfixed, this could lead to a cracked heat exchanger over time, which is a dangerous issue because it could cause carbon monoxide to leak into the home.

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