Has Your Furnace Been Making Strange Noises? 5 Strange Furnace Sounds to Know

Is your furnace making strange sounds? Unusual noises from a home’s furnace can be unsettling, but with a bit of investigation, the cause can often be identified. In order to troubleshoot the issue and take appropriate action, it’s important to become familiar with the common types of strange sounds.



Rattling is typically associated with the furnace blower, specifically the blade hitting something like a foreign object. American Dream property management baltimore explains the rattling sound can also be caused by a motor that’s out of alignment, loose screws or mounting brackets, or a clogged air filter.

If you hear rattling from your unit often and it’s loud enough to be heard more than five feet away, contact an HVAC professional at Furnace repair Toronto to inspect your system and make necessary repairs.


Squealing noises indicate a loose belt or pulley, commonly known as a belt squeal. The belts and pulleys transfer energy from the motor to other components, such as the blower wheel or fan. When these parts become loose or misaligned, the noise will occur and can become worse over time.

To stop squealing noises, you should inspect and adjust the tension of fan belts regularly if your furnace uses them. This can be done by opening the access panel on your unit and inspecting the belts for any damage, dirt/dust build-up, fraying, and/or other signs of wear and tear. If this doesn’t help to stop the furnace noise, then you may need to replace your fan belts. This should only be done by qualified personnel who are familiar with all safety protocols.

Loud Booming

Delayed ignition is caused when the mixture of fuel and air in the burner chamber ignites suddenly instead of burning steadily. This can cause a loud “boom” as hot gases expand quickly due to sudden ignition. When this occurs, it should be addressed immediately because delayed ignition can result in a buildup of carbon monoxide in your home which is very dangerous. Oversized burners can also cause loud booming noises as they take more fuel to complete combustion resulting in an explosive sound as hot gases expand quickly.

A poorly calibrated thermostat can also cause loud boomings when connected to an electric heat pump or two-stage heating system because if the unit is cycling on and off too quickly there may not be enough time for heat exchange and thus causes noises similar to delayed ignition. In order to stop these sounds, you need to make sure that your thermostat is properly set according to the manufacturer’s instructions.

Finally, mechanical issues such as clogged air filters or faulty pilot lights can also lead to loud boomings since they impede normal airflow or combustion process which then creates large and sudden pressure changes inside your unit thus leading to boisterous noise when heated gases escape suddenly and forcefully through restricted openings.


The clicking noise you hear when your furnace is running likely means that its ignition system is working. This type of unit usually uses electric resistance heating, requires a spark in order to ignite the burner, and allows the fuel to mix with air before it’s ignited. It’s quite common for this type of system to make a clicking noise as it attempts to light the burners. If you don’t hear a clicking, then most likely your furnace has an electric spark ignitor, which produces more of a hissing sound instead of a clicking noise. In any case, noises like clicks and whistles are typically normal for many modern units.


Grinding sounds are always caused concern. While many older units tend to generate some noise as a natural byproduct of their operation, grinding could indicate an underlying problem.

A technician will inspect and diagnose the furnace to determine the cause of the grinding sound, and find out if any parts or components require repair or replacement. Common causes of grinding noises include:

  • Malfunctioning blower motor bearings that need replacement.
  • Lack of lubrication on moving parts such as motors and fan blades.
  • Something inside the cabinet has been misaligned.
  • Improperly positioned drain pans under condensate lines in combination with age-related weaknesses (rust-through).
  • Attic vibrations.
  • Radiators out of balance.

Either way, prompt attention is required.


If your furnace has been making noises that it doesn’t usually make, it can be a bit unnerving. This doesn’t necessarily mean that there is an issue with your furnace, but it is important to recognize and address these strange noises so that you can make sure that your furnace is running properly.

Check the Blower Fan

If you hear a loud, sharp banging sound coming from your furnace, it is likely caused by the blower fan. This is one of the most common furnace noises and can occur when the fan becomes unbalanced or stuck in place. If left untreated, this condition will cause further damage to the unit.

Inspect the Ignition System

The ignition system is responsible for turning on and lighting the burners of your furnace when it’s time to heat your home. If your furnace starts making strange noises, your first step should be to check the ignition system. This can often be done in as little as 10 minutes.

Examine the Heat Exchanger

The heat exchanger is an important component of your furnace that helps to transfer heat from the combustion products produced by burning fuel. It is usually a metal box-shaped component found inside your furnace and if this component has become cracked or failed, it could be causing your furnace to produce strange noises.

If you notice any strange noises coming from the exchanger when your furnace is running, it’s important to contact a qualified HVAC technician as soon as possible.

Check the Gas Valve

If your furnace is making strange noises, the first place to check for issues is the gas valve. Gas valves open and close to control the flow of gas into a piece of equipment like a furnace. If it’s not working correctly, it can cause your furnace to make strange noises when it’s on and off.


No matter what strange furnace sounds you may have encountered, it is important to consider the implications and potential hazards that could arise as a result. If any of these sounds persist, it is important to call a technician to inspect your system as soon as possible. A small issue, such as a dirty filter, can quickly grow into larger mechanical and safety problems.

Regular maintenance of your heating system helps you detect issues before they cause expensive damage or disrupted comfort. Contact us for an appointment today and ensure that your home is running at peak efficiency and without the threat of unpleasant noises coming from the furnace.

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