Frightening Noises from the Furnace

Published on: October 16, 2018
Scared boy | Frightening Noises from Furnace | AC Southeast®

Don’t Let Home Mechanical Noises Scare your Friends or Family

A furnace makes some noise with operation, especially older models. These regular noises you hear, such as a slight hum during a heating cycle or the ramp-up of your equipment start cycle, are nothing to worry about. New, strange and sudden noises coming from the furnace or other heating equipment, however, are signs you need HVAC repair.

Start-up Furnace Noises

The following are a few troublesome furnace noises you should listen for this heating season. If you hear them, call a NATE-certified HVAC technician for diagnosis and repair.


  • Clicking. A clicking noise during operation signals an issue with the unit’s flame sensor or problems between the gas supply and furnace ignition.
  • Booms. When a heating cycle first starts, a boom may occur – if this is a regular occurrence, it’s likely nothing to worry about. If the booms are new, a delayed ignition could be the cause. The delay creates a gas build-up in the furnace. You may also notice a natural gas odor nearby your unit.


Operation Furnace Noises


  • Squealing.  Squeals during a heating cycle can spell trouble for the fan motor or fan belts, and requires HVAC repair. Bearings may require lubrication or are worn and need replacement.
  • Chirping. Chirping can occur if your furnace hasn’t been used in a while. After the first several cycles of the season it should resolve. If a chirping noise persists, it may indicate the need for new fan belts or other maintenance.
  • Rattling. Rattling or clanking while the furnace is running is a sign of wear, or loose or broken components inside the unit’s motor or fan.
  • Hissing. Hissing is usually a sign of air escaping the system. You may hear it coming from the walls in your home while the furnace is running. If so, it’s a clear sign you need duct sealing or repair. If the hissing is coming from your furnace area, your filter may be positioned incorrectly or you could be using the wrong size.
  • Scraping. The sound of metal scraping together can indicate issues with the blower wheel. Components may be loose or broken.
  • Popping. Popping noises after ignition are a sign of dirty burners. The pops are a small explosion with potential to actually damage the furnace. They can cause dangerous cracks in the heat exchanger.

Solve Furnace Noises with Preventative Maintenance and Repair

Any time you hear an odd and or new noise coming from your furnace, call your trusted HVAC company for repair. If you continue to operate your heating equipment when it’s making scary noises you may do further damage to your heating system.


This could mean more extensive and expensive repair needs. Resolve issues at the first sign of trouble to protect your comfort and save on repair costs.


Preventative maintenance does wonders to prevent frightening furnace noises. Many of the issues likely to cause these noises are addressed during a routine maintenance tune-up. Always schedule a preventative maintenance heating unit tune-up each fall season to improve performance, efficiency and system longevity.

Get Help with Furnace Noises

If you notice frightening furnace noises, get help today! Contact ACSoutheast.com to find a local heating technician who can diagnose and repair issues causing the strange noises you hear.