Why is my Furnace Making Noises?

Like most things, when things get older they don’t seem to work as well as they used to. Moans and groans echo out, getting more and more frequent. You might be thinking of yourself, but today we are talking about your furnace. What are these noises that your furnace makes and what do they mean?

Furnace noises may vary, but there are three noises that you shouldn’t ignore. These are typically categorized as : banging, grinding, and whining. Here are what these noises mean and what you can do about it.

Banging Noises

If you hear a banging noise when the furnace kicks on, it could be a couple of things. Does it take a little while for your furnace to come on after you call for heat? This delay could be caused by dirty furnace burners. The dirt build-up prevents the burners from igniting. The dirt build-up then creates a build-up of gas. When this gas is then ignited, it causes a loud bang; a mini-explosion. This noise should not be ignored. These small explosions can crack the heat exchanger, which can be expensive to repair.

If you hear the noise several feet from the furnace, then it could be the air ducts expanding as the blower turns on. This can happen for a handful of reasons:

  • Undersized ducts ( talk to a contractor)
  • Closed vents ( Open more vents)
  • Flimsy ducts (brace the ducts)
  • A dirty air filter ( replace the filter if it’s dirty)


Grinding Noises

Loud grinding metal noises aren’t great to listen to or to have. The source of this noise could signal an issue with your furnace’s squirrel cage blower wheel. If you are hearing these types of noises, turn your furnace off immediately to prevent any further damage to the furnace and call a professional for repair. Blower wheel problems include:

  • The blower wheel is loose from the motor wheel ( get a professional to tighten the wheel)
  • The blower is broken and needs to be replaced
  • The motor mount broke, causing the whole blower assembly to drop and hit the housing. 


Whining Noises

This annoying noise 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.
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