Although your Hannibal, MO, furnace will naturally make some noise when it operates, there are some sounds that you don’t ever want to hear coming from the HVAC system. Learn which sounds indicate a failing furnace so that you know when it’s time to call an HVAC technician for maintenance or repairs.

Furnace Whistling

A furnace’s whistling noise comes from airflow restrictions. It’s possible that you simply need to change the air filter to fix the problem. Other potential causes of whistling include:

  • Objects stuck in the ductwork
  • Closed dampers or vents
  • Blocked returns

Whistling can also occur when the furnace isn’t the correct size for your home or the ductwork. Problems with the furnace’s burners or blower can cause whistling sounds, too. It’s time to schedule a furnace repair appointment if you can’t fix the problem by changing the filter.


Do you hear a banging noise when the furnace turns on? There might be an ignition problem where gas builds up within the combustion chamber. The combination of gas buildup and the ignition process causes the banging noise to travel throughout the ductwork.

Ductwork contraction and expansion also causes banging noises. You’ll hear the sounds when the thin metal ductwork material expands while the furnace is operating and contracts as it shuts off.

Clunking Furnace

A misaligned fan is often the cause of clunking sounds. The noise occurs when the fan’s blades touch the walls or other areas of your furnace.

A split or cracked fan belt will also cause clunking noises. Call in a professional technician to find the source of the problem if you’re hearing these sounds.


Do you hear rumbling noises after the furnace switches off? It might be due to gas or oil remaining in the combustion chamber. Ask an HVAC technician to take a look immediately because this can cause indoor air quality problems, with deadly carbon monoxide entering your home’s air.

Are you concerned about any of the above noises coming from your heating system? Contact one of our friendly Air Specialists Heating and Air Conditioning representatives so that we can schedule your next heating maintenance appointment.

Image provided by iStock

Pin It on Pinterest

Compliance Settings
Increase Font Size
Simplified Font
Underline Links
Highlight Links