Furnace Noises and What Could They Mean

Furnace Noises and What Could They Mean

Noises coming from your furnace can mean many things. In addition to sometimes scaring the living daylights out of you, they may signal some other problems that could be coming from your furnace. Some of the issues you can take care of on your own. At other times, due to the risk involved, we recommend consulting a professional. Below are descriptions of furnance noises you may here and what they could mean.


Let’s start with the bang. If you hear a loud bang or a boom coming from your furnace, this could be gas buildup and a delayed explosion. Same thing could happen if you leave the propane gas grill on for a long period of time before igniting it. There might be other reasons for the banging sound and it is recommended contacting a professional.

Deep Rumbling

There are a few reasons that could cause this problem. If you hear a groaning or rumbling noise, it might be an indication something is wrong with your motor bearings, gas burners, or pilot light. A house shaking rumble could be unburnt fuel in the combustion chamber. There is a possibility after shutting off the furnace it continues to burn.  If you hear any groaning or rumbling noise it is recommended to contact a professional immediately.


Now this could mean a number of things. If the rattling comes before your blower turns on, then it could be due to a cracked heat exchanger. This may turn into a serious issue as it is the main cause for carbon monoxide leaks. Best to call a professional ASAP. If the rattling comes after the blower comes on, it could mean there are loose ductwork connections. Another cause of persistent rattling and rumbling could be an imbalanced blower wheel, motor, or a loose screw. Best to contact a professional to take a look.


This sound is probably your ignition kicking on and is normal for your furnace. However, if there is excessive clicking then it could mean there is a problem with your flame sensor. Over time this sensor could accumulate a large amount of dust and debris. You may want to call someone to come in and clean the sensor, or have them replaced.

Scraping Metal

A scraping metal sound could mean there is a problem with your blower wheel. It might be something is stuck in the blower assembly, the blower wheel has become loose, or something might be broken.  Best to call in a professional to take a look and assess what the problem is and provide recommendations what needs to be fixed.


Popping sound is probably coming from your ductwork as the metal expands and contracts. As this is a normal noise, it might be a good idea to schedule a checkup with a professional to take a look and make sure everything is operating properly.


There are a variety of squealing sounds. It can either be an air leak, loose blower belt, motor bearings or malfunctioning blower motor. It is best to have the squealing sound looked into professional and provide recommendations how it needs to be fixed.


This could be due to air leaks or a clogged filter. A few areas to consider checking is has the furnace filter been changed, and inspect your duct system for air leaks. If air leaks are found, or not sure where the whistling is coming from, contact a professional to locate the whistling and provide recommendations what needs to be fixed.

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Vision Mechanical Ltd.