The Most Common Heater Noises and What They Mean

Heaters make a variety of sounds that are very common and normal, but there are some noises that raise concerns. It’s difficult for many people to pinpoint what these sounds mean and how to address any possible issues that might be causing them. In order to get a better idea of what your heating system is trying to tell you through these sounds, listen closely and follow these tips.


Whistling noises are one of the most common strange noises people hear in their heaters. There are a few issues that may be causing this noise, and it’s almost always a fairly easy fix. Whistling noises are usually caused by some form of airflow problem. The first spot you should check is your air filter. If your air filter is dirty and clogged, the restricted airflow through the filter will cause a whistling noise. A quick change of the air filter may solve the problem immediately.

If that doesn’t stop the whistling noise or if the air filter isn’t dirty, the sound may indicate that you have something obstructing the airflow within the ducts. A professional will be able to inspect the ducts and clear any obstructions to ensure that air is flowing properly.

Finally, the whistling could be indicative of a damaged air duct that is leaking air somewhere in the system. An inspection by a professional will be able to locate any leaks and repair them to ensure the whistling stops and that your HVAC system is sealed.


A banging noise is a bit more complicated to both diagnose and rectify, but it’s still a common noise heard in heaters. If the banging noise occurs when you start up the heater, it’s likely due to a dirty burner. When burners get dirty, they’re unable to ignite the gas immediately. A delay in ignition causes the gas to build up. When the gas is finally ignited, so much gas has accumulated that it causes a little burst in the heater that creates a banging noise. Having your burners professionally cleaned or replaced usually clears up this banging issue and will prevent damage to your system.

If the banging noise occurs after the heater shuts off or right after it starts, the noise could be because your metal ductwork is expanding or contracting. If the noise continues, the cause may be that the air filter is clogged or something is obstructing the air ducts or vents, which causes the ducts to bulge due to the excess air. Replacing the air filter may fix the issue. If this does not work, you will have to contact a professional to determine where the blockage is and remove it.


A persistent squealing noise is usually caused by a loose, dry or damaged belt. Tightening the belt, lubricating it, or replacing it will usually clear up this particular noise.

If the source of the noise was not the belt, it might be the bearings. When bearings become old or dirty, they squeal when they turn. Cleaning and lubing them will usually resolve the squealing issue. If not, replacing the bearings may be necessary. Getting a professional involved to deal with this issue is probably wise, as a mistake could end up costing you a lot of money.

If none of those options clear up the squealing, it may be caused by a loose or fallen fan. When the fan is not properly seated, the blades scrape up against the metal and cause a squealing noise. Unfortunately, if the fan is the cause of the squealing, it has likely been damaged to the point where repositioning it won’t be of much help. You will likely need to have a new fan installed.


A rattling noise is common in a lot of older heaters, but it’s possible in newer heating units as well. Rattling noises usually indicate that there are loose parts within the system. Many times, these are loose bolts, panels, or hatches that can be easily tightened back up.

If tightening those parts doesn’t clear up the rattling, it may indicate a more serious issue. Parts deeper within the unit may be loose, the fan belt could be frayed, or the heat exchanger might be cracked. A loose part or a damaged fan belt are serious issues that may cause permanent damage within the unit. A cracked heat exchanger is a dangerous problem that exposes you and your family to possible toxic gas leaks. A professional HVAC service needs to be called immediately to diagnose and fix this issue safely.


All heaters make some degree of humming noise as they operate, but if the humming is particularly loud, it is likely indicating a problem within your unit. The most common source of loud humming sounds within heaters is the motor. While motor problems are cause for concern, this particular sound doesn’t necessarily mean the problem is serious. In many cases, the motor could just be in need of lubrication. However, if lubrication doesn’t stop the humming noise, the motor may be malfunctioning and need to be replaced as soon as possible.


Buzzing noises are very easy to discern from nearly every other noise. The source of most buzzing noises is almost always the electrical system. Specifically, buzzing tends to be heard when the capacitor within the blower motor is failing or a transformer box has come loose. Replacing the blower motor and repositioning or replacing the transformer box will clear up most buzzing noises. This should only be done by a HVAC professional with knowledge of electrical systems.


One of the most alarming noises you can hear coming from your heater is a low rumbling sound. A common issue associated with rumbling noises in older heaters is a malfunctioning pilot light. Check the color of the pilot light flame. If it’s blue, the pilot light is most likely not the issue. If it’s orange or yellow, the flame is too low. Your system will need to be inspected and repaired by a professional immediately in order to function safely.

It’s possible the rumbling noise is also caused by loose parts within the system. Small loose parts cause rattling noises, while larger and heavier parts cause rumbling noises. Tightening these parts should resolve the issue.

Finally, rumbling noises may be caused by excess gas in the chamber that is continuously igniting as the heater runs. This is a severe cause for concern because this recurring ignition could not only cause a house fire, but it can also create a dangerous buildup of carbon monoxide in your home. Shut off the heater and contact a professional HVAC service immediately to fix this problem safely.

Contact the Professionals

No matter what noise your heater is making, diagnosing and repairing heater problems is a complicated and potentially dangerous job that requires professional technicians to resolve the issue safely and effectively. Our experienced team at Charleston Heating and Air will provide you with fast, efficient, and skilled service to fix any troublesome heater noise. We also provide repair, maintenance, and installation services for all heating and cooling systems. In addition, we are water heater and electrical system specialists. If you’re in the Charleston, South Carolina, area and would like to learn more about resolving noise issues in heaters or any of the other services we provide, contact us at Charleston Heating and Air today.

company icon