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Douglas Cooling & Heating Blog

What it Means When Your Furnace Makes Weird Noises

furnace-techIf you’ve had your furnace for a while, you probably know what it’s supposed to sound like when it’s running. If your furnace suddenly starts to make rather unusual noises, that is not something you should ignore. Strange noises are often one of the first signs that homeowners notice that something isn’t right with the furnace. If you ignore the signs, you may end up having to pay a lot more in repair costs or even replace your entire system. Have a look below at some of the descriptions of weird furnace noises you may encounter, and what they mean.


Inside your furnace is a part called the air handler, which is responsible for circulating air throughout the home during operation. The air handler is put under a lot of strain while it’s operating, which is why it contains a number of bearings to help reduce friction. The bearings help the air handler to run smoothly, but they do wear down over time. As the bearings get closer and closer to failing, the friction on the air handler increases. Eventually, the handler may start to make a loud grinding sound while it’s running. If you hear this sound, you should have a professional examine your furnace right away. If you wait, the air handler motor may completely burn out and need to be replaced.

Short Cycling

If you hear your furnace turning on and off every couple of minutes instead of completing a full heating cycle, then you’ve got a big problem. That is called short cycling, and it poses a serious threat to the health of the furnace. Short cycling reduces the amount of output the furnace can generate, because it prevents the system from completing heating cycles the way it needs to. However, it also causes the furnace to wear down much faster than it normally would. The longer a furnace is left to short cycle, the more damage it’s going to incur and the more likely it will be to break down in some way. You need to make sure that you have a professional technician look at your furnace as soon as possible after you notice this sound.


If you’re using a gas furnace, and it makes a loud booming sound every time it turns on, then it’s probably suffering from delayed ignition. This happens when the burner assembly becomes clogged with carbon particles, a common occurrence in furnaces that have been in use for a while. Clogged jets in the assembly ignite later than they are supposed to, and when they do ignite they burn through a lot of extra gas at once. That’s what causes that booming sound. Having a professional clean out the assembly for you should solve the problem. Just make sure that you have it done soon, before the assembly becomes completely clogged.

Douglas Cooling & Heating provides comprehensive HVAC services in Shelby County, AL. If you need help with your furnace, contact us today to schedule an appointment.  

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