Why Is My Furnace So Loud?

Furnaces generally aren’t noisy as they run. They normally produce a click at the start of the heating cycle and steady ambient noise as the blower and burners work, but a furnace’s location in the home often helps dampen any natural operating noise. Wondering, “why is my furnace so loud?”,  is a good sign there may be something wrong within your heating system. Hans Heating & Air shares the issues that can cause a noisy furnace as well as what needs to be done to silence that sound.

Why Is My Furnace So Loud?

Anytime you find yourself asking, “why is my furnace so loud?”, it’s important that you don’t ignore the sound. Furnaces generally don’t produce any noises outside of their usual startup and operating sounds unless there is a malfunction or issue somewhere within the system. While there are some furnace noises that can occur suddenly that don’t signify a serious issue, most loud furnace sounds that come on suddenly are something you should be concerned with.

A loud furnace is an unhappy furnace. Finding the cause of the furnace noises will ultimately solve your issue. Learn what sounds don’t require calling a professional and which noises mean you want to schedule furnace repair service right away.

A Big Bang or Boom

If you hear a loud banging noise or booming sound shortly after the furnace turns on, it is likely the result of a small explosion within the unit. This noise and the explosion are caused by a system problem known as delayed ignition. If your furnace burners do not ignite the fuel as it enters the combustion chamber, the gas will start to build up within this space. Once burners ignite, their flames ignite the gas and produce the loud noise you hear.

This furnace noise is typically linked to blocked gas ports that have become clogged by corrosion and rust due to moisture buildup in the system. Another reason you might hear these furnace noises is an accumulation of dust and lint within the furnace. Sulfur from natural gas combustion can also build up in the unit and clog the burners or the pilot light. The big bang may also be caused by problems with gas pressure or faulty electronic ignition components. These issues require professional heating repair.


Hearing a high-pitched squeal as the furnace runs is a sign of a belt issue in the blower assembly. The belt that sits on pulleys attached to the furnace blower motor and blower fan may have slipped or sustained some kind of damage. Some homeowners feel comfortable adjusting belt tension themselves to fix a slipped belt, but if you aren’t comfortable doing so or the belt needs to be replaced, call your HVAC company to make repairs.


A noise that resembles grinding as the furnace operates is probably coming from a worn-out ball bearing within the blower motor. Typically, the motor bearings are lubricated during annual furnace maintenance. If your furnace hasn’t received regular maintenance, call your HVAC technician for service. Let them know about the loud noises you hear coming from your furnace. Schedule your yearly heating system tune up now to address these loud noises. 


A whistling sound from your furnace while it runs can indicate an airflow restriction. A dirty air filter is a common cause of air flow restriction through the system. Check your air filter and replace it with a new one if the filter’s surface is completely filled with particles.


When your furnace produces a scraping sound, like metal against metal sound,  this is a sign that a component may have come loose inside the unit. The cause of your noisy furnace is most likely that a faulty part is hitting other equipment inside the furnace. Turn the system off and call for repairs right away before the loose part causes severe damage to other components.

Furnace Repair in Montgomery, AL

If you’ve been wondering, “why is my furnace so loud?”, the information above should give you some good insight into what is happening inside your system. If you hear one of the noises described above, call Hans Heating & Air right away to schedule furnace repairs.

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