Unexpected Furnace Noises (and What They Mean)

When your furnace is running during the fall and winter, it should be smooth, efficient and quiet.

If it sounds like there’s a party going on inside, something’s definitely wrong.

Ignoring funky furnace sounds because “it’s always done that” or “they always go away” is risky and dangerous.

In some instances, it could ruin your unit beyond anything a furnace repair can do.

So the next time your furnace makes any of the following noises, make certain you contact us at ABW Halton ClimateCare immediately.

Blower wheelA loud, abrasive scraping sound

Something that sounds like metal on metal (or worse, nails scratching a blackboard) rubbing against each other could indicate a problem with the blower wheel.

  • If you hear this noise, turn off your furnace ASAP and call us

The blower wheel is responsible for blowing air out of the furnace and throughout your home. The wheel is attached to a motor shaft using a set screw.

That metal-rubbing-metal sound could be caused by:

  • The wheel detached from the shaft. Now, the wheel is banging against the blower casing. If damage is minimal, a furnace maintenance visit can tighten it right back up.
  • The blower wheel is broken. Nothing to do here but get it replaced.
  • The motor mount is busted. This is quite serious, actually. That’s because the entire blower assembly unit has fallen and has hit (and potentially damaged) the housing.

Bang or pop when the furnace gets turned on

There are two main culprits behind those banging or popping sounds:

Air duct

1. Expanding and contracting air ducts that are commonly found in metal ducts.

As the blower turns off and on, the ducts expand and contract in time.

Usually, this is caused by ducts that are too small (undersized), closed vents, weak or flimsy ducts, or a clogged air filter.

2. Dirty burners which prevent them from igniting immediately. That little delay causes a tiny amount of gas to build up. That banging sound is actually the gas igniting.

That’s dangerous and needs to be addressed immediately.

Over time, these little explosions can crack the heat exchanger, which can be quite costly to repair.

Air ductHigh-pitched squealing or whining sound

Compared to the other sounds listed in this blog, a squeal or whine is more of a nuisance than an actual danger.

That said, it’s still best to get it looked at.

More often than not, this grating noise is caused by:

  • Blower belts that have come loose, slipped, or frayed (if it’s the latter, then it needs to be replaced outright)
  • Dry shaft bearings that need oiling in the appropriate ports
  • Blower motor malfunction that requires repairing or replacing

Hear any of these sounds? Give us a call

Don’t attempt to open your furnace and fix the issue yourself. Behind the casing is a complicated piece of machinery that’s buzzing with electricity and fumes.

You could make the problem worse or even hurt yourself in the process.

Conversely, if that strange noise is minor at the moment, it could become a big problem down the line.

The safest, surest way to quiet a noisy furnace is to contact us and tell us what’s going on. We’ll get back you ASAP to discuss the issues with your furnace.

Contact us