Furnaces have a distinct sound when they are in operation. However, when your furnace makes noises that are unfamiliar such as a huge thud or constant clunking, clicking, humming, or other sounds, it is likely that there’s something wrong with it. Here’s why your furnace is making noises and tips on how to troubleshoot it.

Rumbling Sound

This particular sound depicts an issue with the combustion chamber as the fuel is continuing to burn inside the burners when they are shut off. This indicates an issue with the flame sensor, pilot light, or burner and requires immediate repair to prevent carbon monoxide poisoning.

Grinding and Scraping

Oftentimes, metal against metal produces grinding, scraping, and clanking sounds and could point towards something serious. For instance, it is likely that the blower wheel is rubbing against the blower house casing or it has become loose producing such sounds. A blower fan rotates continuously when in operation and thus requires abundant lubrication and maintenance for long life and durability. Reaching a certified technician can fix the problem before it is too late.

Thumping Sound

A thumping sound usually indicates an unbalanced blower motor or wheel. This could cause potential damage to the wheel or the motor and the housing as a whole and thus, requires immediate repair to fix the issue once and for all. This is one of the many reasons behind a furnace making noises.


A blower motor is responsible for pushing warm air through the ducts and thus, it is a crucial component. If you hear a squealing sound, it is likely that the blower motor is to be blamed. This is because the blower motor requires routine lubrication without which it will produce a squealing sound before eventually breaking down. A loose belt in the blower motor can produce a squealing sound as well. Issues related to shaft bearings produce a similar sound.

Loud Humming Sound

There are a few possible reasons why you could be hearing a loud humming sound apart from the usual humming when a furnace is running. It indicates there’s some issue with the fan or the capacitor. It could also be an issue with the heat exchanger due to a clogged air filter, blower, among other components. A loose screw can cause a humming sound as well.

Repeated Clicking

If the furnace produces repeated clicking after it has settled, something at the control panel or the compressor requires attention.

Popping Sound

If your furnace is producing popping noises, it could happen when a blower motor pushes warm air through the air ducts, this triggers inflation as the air reaches the cold air inside the duct causing the metal to enlarge and thus, producing the popping sound. On the other hand, dirty gas burners due to the accumulation of sediments over time can cause popping sounds. Thus, thorough cleaning of gas burners from time to time is recommended. It can also produce loud bangs.

Whistling Sounds

If your furnace produces a whistling sound when it is running, it is likely restricted airflow due to a clogged air filter. Turns out cleaning the air filter isn’t a strenuous task. Watch some YouTube videos to fix it up or dial Capital Plumbing in Canada for assistance.

If you find any of the furnaces making noises the same as what your furnace is making, you will need an expert’s help such as the folks at Capital Plumbing. It is always better to let the pros do their job while you sit back and relax.