Why Is My Furnace Making a Banging Noise?

Published On December 30, 2022


Houses make noise, from creaking floors and walls to refrigerators, fans, and freezers. Not all noises signal trouble, but when the furnace fires up and all the banging starts, you might just think your home is about to launch itself to Mars, or crash down on top of you.

Most furnaces make some kind of noise during operation, and it’s not uncommon to hear yours when it starts up and shuts down. Some of the sounds you hear come from the furnace itself, and some come from the ductwork. In any case, only certain noises indicate a real problem with your furnace.

Dirty Filter—Usually the filter is the first thing to check when you suspect problems with your furnace. As it cycles, your furnace pushes air to the living spaces of your home, but a dirty or incorrectly sized air filter will hinder the flow of air and create a backlog of heated air, which expands the metal in the system. When the furnace stops, you’ll hear a “bang” as the metal cools and assumes its original shape. A new air filter will fix this problem.

Dirty ductwork will also cause a backup of heat in the system, and will make noise when it cools and contracts.

Dirty Burners—Dirt, dust, carbon buildup, all these can compromise the burners of your furnace, and when that happens you’ll hear a loud bang when your furnace starts up. Dirty burners are subject to “delayed ignition,” a situation that involves a buildup of gas because of obstruction. The bang occurs when the excess pocket of gas finally ignites. This problem requires attention; it could lead to serious damage to the entire heating system, and could even result in a fire.

Delayed ignition can also be caused by a defective ignitor, low gas pressure, or insufficient flame on the pilot light.

High-pitched Squealing—When you wake up in the middle of the night because you hear something like a giant troll scraping its fingernails along a blackboard, there’s a good chance the belts of your heating system are failing. It’s not a serious problem, but you’ll want to make the fix before the belts go out completely, which would cause the furnace to stop altogether.

Most furnace problems can be easily fixed, and the experts at Colley Refrigeration are just the technicians who can do it. Don’t wait until the minor fix becomes a major fix. Reach out to us at the first sign of trouble!

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