Why Is My Furnace Making Strange Noises?

John Turpin is our resident home service repair expert here at Service Direct. He’s got the knowledge and experience to help homeowners like you make sense of most home repair issues. And with Service Direct, we connect you with top-tier service professionals to help with any repairs needed.

Don’t Panic When You Find Your Furnace Making Strange Noises

You’re worried and can’t help but ask, “Why is the furnace making strange noises?” It’s common for the heater to make noises, typically low sounds, while it is operating. But if you hear loud, strange noises that weren’t there before, something might be wrong with your furnace and it might need to be checked out.

Keep in mind that a dull hum, and a pop or a click, are normal when the heating cycle starts. However, they usually end up getting a bit louder as the furnace gets older, when wear and tear increases. Still, it’s good to know about the possible reasons you’re hearing these weird sounds, in order to know if it’s a minor problem or needs professional assistance.

Sounds from the Furnace and Why You Hear Them

Banging or Popping Sounds

If you hear loud banging or popping sounds when your furnace turns on or off, it could be a sign of dirty burners or delayed ignition. Over time, dirt and debris can accumulate on burners, hindering their proper functioning. When the furnace ignites, the buildup of gas can result in a small explosion, leading to these noises. Delayed ignition can be caused by a faulty ignition system, which may need repair or replacement.

Squealing or Screeching Noises

High-pitched squealing or screeching sounds often indicate a problem with the furnace’s blower motor or belt. The blower motor may be experiencing issues due to a lack of lubrication, worn-out bearings, or a damaged belt. Ignoring these sounds can lead to further damage and reduced efficiency. It’s essential to address them as soon as possible by scheduling a maintenance visit with a professional technician.

Rumbling or Booming Sounds

Why is your furnace making strange noises, specifically rumbling or booming sounds? These sounds could signify a problem with the furnace’s heat exchanger. The heat exchanger transfers heat from the burner to the air circulating through your home. The problem is that cracks or gaps can develop in the heat exchanger over time, allowing combustion gases to escape into the surrounding area.

The gases that escaped can create the rumbling or booming noises you hear. Keep in mind that a damaged heat exchanger is a serious issue as it can lead to carbon monoxide leaks, posing a significant risk to your household’s safety. If you suspect a problem with your heat exchanger, turn off your furnace immediately and contact a professional technician for inspection and repair.

Whistling or Hissing Sounds

Whistling or hissing noises could indicate air leaks or issues with the ductwork. Leaky ducts can disrupt the airflow, causing the furnace to work harder to maintain the desired temperature. This strain on the system can result in whistling sounds.

Similarly, you may be hearing hissing noises as a result of leaks or gaps in the ductwork, which allow air to escape. It’s advisable to have a professional HVAC technician inspect the ducts and address any leaks or damaged sections.

Clicking or Tapping Sounds

Furnaces often produce clicking or tapping sounds during their normal operation. These noises usually occur when the system starts up or shuts down. But if the clicking or tapping becomes more frequent or unusually loud, it might indicate a problem with the ignition system, a faulty thermostat, or issues with the electrical components. It’s best to have a technician evaluate the furnace to diagnose and resolve the underlying cause.

Our resident home repair guru, John Turpin, has provided a list of common reasons why your furnace is making odd sounds as well as some expert tips on how to approach the solution.

Grinding or Metal-on-Metal Sounds

Why is the furnace making strange noises? If it’s grinding or metal-on-metal sounds, there’s a good chance your furnace has a serious problem. These sounds often point to a malfunctioning blower wheel or motor. If the blower wheel becomes loose or damaged, it can scrape against other components, resulting in a grinding noise. Continuing to run the furnace in this condition can cause further damage and potential system failure. In this situation, it’s crucial to shut off the furnace and contact an HVAC professional.

Sudden Changes in Sound

So, your furnace sounded normal, but then it suddenly started making unusual noises. When this happens, it may be a sign that the furnace is failing. It may have a worn-out belt, motor bearing, or fan blade, causing sudden changes in sound. Pay attention to any new or distinct noises and schedule a maintenance visit promptly. Addressing the issue early on can prevent more extensive damage and costly repairs.

Animal or Debris Intrusion

Occasionally, strange noises may be the result of animals or debris finding their way into your furnace system. Small critters like mice or birds can build nests or get trapped in the ductwork, leading to scratching or chirping sounds. Debris such as leaves or twigs can also enter the system and cause rattling or buzzing noises. If you suspect an animal or debris intrusion, it’s best to contact an HVAC professional to remove them safely.

Rattling or Vibrating Sounds

My heater is making a weird noise, what do I do? If you notice a rattling or vibrating noise coming from your furnace, it could be due to loose components or unsecured ductwork. In such a case, you should check the panels and access doors to ensure they are tightly fastened.

Loose screws or bolts can create rattling sounds as the furnace operates. Also, inspect the ductwork for any loose sections that may need to be reconnected or sealed properly. Addressing these issues can help eliminate the noise and improve the efficiency of your furnace.

Lack of Maintenance

Regular maintenance is vital for the smooth operation of your furnace. Neglecting routine maintenance tasks like cleaning or replacing air filters, lubricating moving parts, and inspecting electrical connections can contribute to unusual noises. Proper maintenance not only reduces the chances of strange sounds but also improves energy efficiency and extends the lifespan of your furnace.

Hire a Local HVAC Pro

Remember, diagnosing and repairing furnace issues can be complex. This is why we always recommend seeking assistance from a qualified HVAC technician. They have the expertise and tools necessary to identify and resolve problems efficiently and safely. Contact one a local pro using the phone number or form on this page to address the problem today.