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Mike Smith Heating & Air Conditioning, LLC Blog

Why a Rumbling Furnace Is So Bad


Your furnace can’t simply ask you for help when it’s not doing well. But if you pay attention, it will give you some signs that it’s having trouble. One of the easiest signs to notice is when your furnace makes an unusual noise.

There are a variety of sounds that can indicate a problem. If you’re hearing a rumble from your furnace, this is a particularly important one to have checked out. Here’s what might be going on.

Incomplete Combustion

A few different problems can cause the fuel your furnace is using to be burning unevenly. This could be a dirty burner that simply needs cleaning, which would ordinarily be done during the course of regular maintenance. But it could be something much more serious.

The pilot light may be too low, not allowing for proper ignition. There may be a breach somewhere in the gas line that is allowing other gasses (air) to infiltrate, so the natural gas is not pure when it is ignited. There could even be a crack in the heat exchanger. 

The heat exchanger is the component that keeps the combustion gasses separate from the air you breathe. It contains the heat and warms the air that passes around it, which is then sent through your ductwork and around your home. If combustion gasses are able to leak from the heat exchanger, carbon monoxide can escape into your air, which is extremely dangerous.

Check the color of your pilot light. It should always be blue, never yellow or orange, which can indicate that carbon monoxide may be leaking from your system. Check your carbon monoxide detectors. If your flame is blue and your carbon monoxide detectors are working well and not signaling a problem, you still need furnace service in West Monroe, LA.

If your flame is not blue, if you do not have carbon monoxide detectors or realize they may not be working properly, if you notice soot buildup inside your furnace or a clicking sound after a heating cycle while the system is cooling down, your problem is urgent, and you should get help immediately. 

Motor Problems

Another sound that some people describe as a rumble might be a much less dangerous issue, though one that still requires repair. If the rumble sounds more like mechanical parts rubbing together or groaning rather than like gas burning loudly, it could be friction inside the blower motor.

The blower motor powers the fan that pushes the warmed air through your ductwork. To keep it moving smoothly, it contains bearings. During maintenance, these bearings are thoroughly lubricated. Lack of lubrication or wear and tear over years of operation can cause these bearings to wear down and grind together.

The biggest risk here is that the friction could cause the motor to overheat and burn out, sometimes literally fusing the wiring together. Before it gets quite that hot, the limit switch might just shut the whole system down when it senses the heat. Either way, your furnace will have broken down completely, and the motor will have to be replaced.

To avoid that, catch the problem early, so that all your technician will need to do is replace and lubricate the bearings themselves. If you hear this sound, or any other unexpected noise from your furnace, addressing the concern promptly can help to keep repairs—and costs—minimal.

Contact Mike Smith Heating & Air Conditioning, LLC. We provide “Professional grade service.”

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