March 22, 2023

What Does it Mean When Your Furnace Makes Noise?

what does it mean when your furnace makes noise

What Does it Mean When Your Furnace Makes Noise?

Do you dread entering a room to hear your furnace rumbling in the background? It can be unsettling when hearing strange noises coming from what is usually a reliable machine. But instead of avoiding it, why not explore what could be causing such loud noise from your furnace? Knowing what does it mean when your furnace makes noise can help you determine what steps to take next and whether you need professional assistance.

Common noises coming from furnaces include intermittent pops or cracking as air pockets move through the air ducts, while booming/rattling and metallic grinding noises can signal more serious issues with the furnace.

Let’s take some time to diagnose this issue.

Normal Furnace Sounds

Is your furnace making strange noises? Don’t worry because it is likely within the range of typical furnace sounds. Furnaces make various popping and cracking noises as air pockets move through the air ducts when heating up and cooling down. It is generally normal, although a loud banging noise could indicate an issue with your water heater or air conditioning unit.

A few common noises are associated with a healthy furnace, and these include: 


Most furnaces hum while running, indicating all is well within the system. If the hum is louder than normal or there’s an obvious change in its pitch, however, it could mean there’s something wrong, and you should contact a professional immediately. 


Clicking is another sound that may come from your furnace, especially when it first turns on. This noise often originates from relays or switches as they close and open to start the blower motor or ignite the burners. Again, if this clicking noise seems louder or more frequent than usual, it could indicate an issue with your system that requires professional attention. 


You should also expect to hear air from the vents when the blower motor kicks on and off throughout a cycle. This blowing sound often changes in volume and intensity depending on how far along in the cycle you are; for instance, some homeowners may notice more of this sound at their vents during startup than at other times in the cycle. Again, if any of these sounds seem out of place, such as being too loud or last too long, then it’s important to have a technician come out for diagnostics.  


If you notice whirring from your furnace (especially if accompanied by a burning smell), shut off power to your unit immediately and contact an HVAC technician immediately, as this could indicate severe damage within the system due to overheating or other issues.  

Abnormal Sounds to Listen For

It’s important to listen closely when your furnace turns on to detect any unusual sounds that could indicate an issue that needs to be addressed by a professional technician. Here are some sounds that may require attention:

High-pitched squeals

It could mean something’s wrong with your blower motors, such as worn bearings or motor belt issues. It’s best to call a technician as soon as possible for repair/replacement before further damage can happen.

Booming or rattling

A rattling noise could mean something is loose or just needs cleaning from dirt/dust buildup on moving parts like fans or blowers – most likely requires maintenance from an expert HVAC technician who can diagnose the exact problem and make necessary repairs safely. It’s also possible that the boilers need cleaning, which requires professional help due to their complexity, such as the risk of carbon monoxide leaks, etc.

Banging or knocking

If you hear loud banging or knocking from inside the furnace cabinet or surrounding area, turn off the power immediately and call an HVAC technician as soon as possible. Several problems, including blocked vents or ductwork, a faulty motor, worn-out bearings, or other issues with internal components such as fan blades or belts, could cause it.

Metallic Grinding Noise

If you notice grinding noise coming from your furnace, it could mean one of two things: debris has collected around one of the moving parts (like fan blades), which will need removal by an expert HVAC technician who can access all areas safely. Alternatively, it may signal more serious problems, such as bearing failure, requiring immediate action and fast replacement before more damage occurs.

Loud rumbling

Loud rumbling noises can occur when dirt builds up inside the burners, restricting airflow. Still, they can also be caused by other problems, such as loose screws or bolts rattling inside the cabinet or failing electrical components shorting out due to wear and tear over time. In any case, if you experience loud rumbling noises from your furnace, contact an HVAC technician immediately for further inspection and repair work if necessary.


Noise coming from your furnace is an indication that something is wrong. Generally, a loud banging or squealing sound may be caused by loose bolts, worn fan motors, frayed belts, and more. If your furnace suddenly starts making odd noises, it would be best to contact an HVAC technician as soon as possible to investigate. Don’t try to repair the furnace yourself. It could potentially cause injury or further damage to the unit.

Remember, a properly maintained furnace is essential to your home’s comfort and energy efficiency system. Plus, regular maintenance can help you catch minor problems before they become bigger issues down the line. Knowing what noise causes can help you diagnose the issue quickly and accurately determine how best to repair or replace your furnace to get back up and running again quickly and safely.