Why is My Furnace Making Strange Noises?

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Furnaces are fairly noisy systems during operation. If you’ve had your furnace for a while, though, you’re probably familiar with the kinds of noises it tends to make. If your furnace begins to make unusual noises of any kind, it often indicates a problem with the system. Let’s take a look at some of the unusual furnace noises you may hear at some point in your system’s lifespan, and the problems they indicate.


The furnace uses a part called the air handler to circulate air throughout the house. The part is essentially a large motor with a fan attached to it. A lot of friction is generated by the motor during operation, so to help cope with it the system is equipped with a number of oiled bearings. These bearings lessen the friction greatly, but they do wear out over time. As the bearings wear down, the friction on the air handler increases and produces a loud grinding sound. If you hear this sound, you should have the bearings in your furnace replaced as soon as possible. Otherwise, the air handler motor may overheat and burn out.


If you’re using a gas furnace, and it’s making a loud booming noise when it starts up, then you probably have a dirty burner assembly. As the burner assembly burns gas, carbon particles will build up on the jets. Eventually, the carbon buildup can get so bad that it actually prevents one or more of the jets from firing on time. When the jets finally do ignite, they burn through a large amount of gas at once and generate a loud boom. Getting your burner assembly cleaned by a professional will fix the problem.

If your furnace is making strange noises, or you need any other kind of furnace repair, call Bell Plumbing and Heating. We offer a full range of furnace repair services in Denver, CO.

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