Why is My Furnace Making Weird Noises?

Monday, April 16th, 2018

BurnerIf you’ve had your furnace for a season or two, you probably already know what it sounds like when it’s operating normally. If the system begins to make unusual noises while it’s running, that’s typically a good indication that something is wrong. You should call a professional to examine your furnace and make sure that everything is operating properly. While you’re waiting, though, have a look at some various noises that may indicate a problem with your furnace.

Loud Booming

If you’re using a gas furnace, and it’s making a loud booming noise every time it starts up, then it’s probably having an issue with delayed ignition. Gas burner assemblies tend to suffer from carbon buildup over time, as a natural byproduct of combustion. As the carbon buildup reaches high levels, it can partially clog the jets in the burner assembly. Once the jets become clogged enough they will have trouble igniting when they’re supposed to. The jets will finally ignite later than the rest of the assembly, and burn through the excess gas all at once. This is what causes the loud booming sound. You’ll need to have a professional clean out your burner assembly for you, before it becomes completely clogged and fails to ignite at all.


The furnace contains a part called the air handler, which is designed to circulate air through the ducts while the system is operating. Inside the air handler motor are a number of oiled bearings, which help the system to run as smoothly as possible. The bearings don’t last forever, though. As the bearings wear down over time, the friction on the air handler motor will increase until it begins to make a grinding sound while the furnace is running. If you hear this happening, you should make sure to call for repairs as soon as you can. If the bearings fail completely, the air handler motor could easily overheat and burn out.

Short Cycling

Short cycling is what happens when the furnace overheats, or is experiencing an electrical issue that is throwing off its operating rhythm. The system will start, run for a couple of minutes, and then shut off without having completed a full heating cycle. This seriously hampers the amount of output the system is able to generate, but it also increases the amount of wear and tear on the system significantly.

The longer a furnace short cycles, the more prone to developing problems it will become. Short cycling for long periods of time will also shorten the effective lifespan of the furnace, possibly by years. For these reasons, it’s highly recommended that you call for repairs as soon as you notice your furnace short cycling. The faster you react, the more damage you can prevent.

Comfort First Heating and Cooling, Inc. provides comprehensive furnace repair services throughout Joliet, IL. If you need help restoring your furnace to proper function, contact us today for an appointment with one of our professional technicians. We’ll make sure that your furnace serves you well.

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