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furnace makes noise when heat is on

During the cold winter days, furnaces are our reliable sources of warmth and comfort. However, what happens when it makes strange noises when you turn on the heat? This situation can be troubling and leave you wondering if something is wrong with the furnace. The truth is furnaces can make various noises, and not all require immediate attention or repair. Understanding why your furnace makes noise when heat is on can help determine if it is a cause for concern or if it is just a normal part of furnace operation.

In this blog post, we will explore the common causes of furnace noise, the different types of furnace sounds, and what to do if your furnace makes noise when the heat is on. You can better diagnose and address furnace-related issues by understanding what causes furnace noise. This knowledge will enable you to take the necessary actions and work towards maintaining a comfortable home environment during the cold winter months.

Causes of Furnace Noises

Furnace noise can be linked to various reasons, including loose ducts, worn-out parts, and dirty filters. 

Loose Ducts

One common cause of furnace noise is loose ducts, causing them to vibrate and create noise when air is forced through them. This noise can be amplified when the ducts are mounted on walls or ceilings. Loose ducts can also lead to uneven heating and increased utility costs. One of the signs of loose ducts is a rattling noise from your furnace.

To fix the issue of loose ducts:

  • Inspect your ducts for any visible defects or damages
  • Reinforce and secure them using duct tape
  • Contact a professional to inspect and repair the ducts if necessary

Worn Out Parts

Another common cause of furnace noise is worn-out parts. Moving parts such as the blower motor and fan blades are susceptible to wear and tear over time. It can cause the components to loosen or become damaged, resulting in noise when the furnace runs. For instance, a worn-out fan belt can stretch out and become loose, making a high-pitched squealing sound.

To fix the issue of worn-out parts:

  • Inspect the furnace’s components, including the blower motor, fan blades, and bearings, for visible wear or damage.
  • Replace damaged parts promptly.
  • Schedule regular maintenance service checks with a furnace repair professional to help detect and replace worn-out parts.

Dirty Filters

Dirty furnace filters can also cause noise when the heat is turned on. Accumulated dirt and debris can obstruct the airflow, creating a sucking sound as air is drawn through the clogged filter. Additionally, a clogged filter can decrease energy efficiency, longer operating times, and costly utility bills.

To fix the issue of dirty filters:

  • Check your furnace filter regularly, and replace it with a fresh one when necessary.
  • Routinely schedule maintenance checks for your furnace filter with a heating professional to ensure it works optimally.
  • Consider upgrading to higher-efficiency air filters, which trap more particles and require less frequent replacement.

Different Types of Furnace Noises

Furnaces can make different types of noises depending on the underlying issues. Understanding the different types of furnace noises can help you diagnose the problem, mitigate costly repairs, and restore your furnace to working condition.

Here are different types of furnace noises and identify their possible causes.


A high-pitched squealing sound can indicate a worn-out blower motor or fan belt. Over time, the belt can stretch out and become loose, causing it to slip and create a squealing sound.

Another cause of a squealing noise is unbalanced blower wheels, typically caused by dirt and dust accumulation. As the wheels rotate, they may hit other stationary parts of the furnace, resulting in a squealing sound.


A dirty burner can cause a deep rumbling sound. Dirt build-up inside the furnace can cause uneven flames, making the furnace rumble.

A rumbling noise can also be linked to unbalanced blower wheels that may cause the furnace to vibrate and make noise.


A screeching sound can be caused by a damaged fan blade, which may be bent, misaligned, or worn out. When the blower is turned on, the blades rotate, causing them to hit adjacent stationary parts.

Another possible cause of the screeching sound is worn-out motor bearings. As the motor rotates, it may cause a whistling sound as it grinds against worn-out bearings.

What to Do If Your Furnace Makes Noise When Heat Is On

Furnace noise when the heat is on is a common problem that can make your home environment uncomfortable. If you’re experiencing this issue, it’s essential to take immediate action to identify the cause and fix any underlying problems.

Check Air Filter

One of the first things to do if your furnace makes noise when the heat is on is to check your air filter. Clogged or dirty air filters can cause whistling or sucking noises as air is drawn through the furnace. If you notice any visible dirt or debris, replace it with a fresh filter.

Inspect Your Furnace

If changing the filter does not resolve the noise issue, consider inspecting your furnace. Check for any signs of wear, such as bent fan blades, loose parts, or visible duct damage. Loose or dirty parts can cause a variety of noises, including rattling, banging, and screeching. If you’re unsure what to look for, refer to your furnace owner’s manual or call a professional.

Call a Professional

If you cannot identify the cause of the furnace noise or if the problem persists after inspecting your furnace and changing the filter, it may be time to call a professional. Service technicians are trained to diagnose and fix furnace-related issues quickly and efficiently. They can also perform regular maintenance checks to ensure the proper functioning of the unit and detect any potential issues before they become significant problems.


Furnace noise when the heat is on can indicate a potential underlying issue. Regular air filter changes, maintenance checks, and prompt action if any issues arise are the best way to keep your furnace running smoothly. If you’re experiencing furnace noise or other unusual signs, don’t hesitate to call a professional for help. You can prevent costly repairs and enjoy comfortable winter temperatures with adequate care and maintenance.

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