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What's that noise coming from my furnace?

What's that noise coming from my furnace?

Many homeowners ask, “Why is my furnace so loud?” Furnaces can make a variety of noises for different reasons. How do you know which ones you should worry about? In this article, we go over some different sounds that can come from your furnace, what they mean and what to do about them.


  • Loose, slipping, or fraying blower belt – Adjust or replace the belt.
  • Unlubricated shaft bearings – Oil moving parts.
  • Malfunctioning blower motor – Fix or replace the blower motor.


  • Small holes or gaps in the ducts – Seal ducts.
  • Clogged filter – Change the filter.
  • Undersized ducts – Get new ductwork that is the right size.


  • Loose parts and/or screws – Over time parts and screws can become loose. Tighten loose screws.
  • Cracked heat exchanger – As your furnace heats up and cools down, the metal surfaces will naturally expand and contract, and over time, the exchanger will crack. Replace the heat exchanger.


  • Dirty furnace burners – Delays furnace from igniting causing excess gas buildup. Clean furnace burners or have professional help.
  • Expanding and contracting air ducts – Caused by undersized air ducts, closed vents, or a clogged air filter. Change the filter, make sure the vents are open, and check your ductwork.

Scraping (metal against metal)  –  Immediately turn off your furnace!  Allowing the furnace to operate when there is a problem with the blower wheel could cause further damage to your equipment.

  • 1. Blower wheel loose – Could be hitting the blower casing. Depending on the damage, a professional can tighten the wheel or may need to replace it.
  • 2. Blower wheel broken – Replace the blower wheel or have a professional replace it for you.
  • 3. Motor mount broke – This can cause the whole blower assembly to drop and hit the housing. The wheel may need to be tightened or replaced.

Furnaces often make noises, especially older ones. Some sounds may not be cause for concern like minor pops from the ducts and humming as the blower runs. If the noises are unusually loud and frightening, you definitely should have a professional check them out. It’s better to be safe than sorry because a minor repair can turn into a major repair that will end up costing you a lot of money.

Right Now Air & Solar is here to help you if you are concerned about the noises coming from your furnace. We recommend having your furnace tuned up every year before winter to make sure it’s in safe working condition. To request furnace service, contact us.