Why does your ductwork make banging noises? Noise isn't always indicative of HVAC problems because ducts always expand and contract, but read more to find out.
The 5 Most Common Reasons Your Furnace is Making Loud Noises
Keep your ear out for whistling, buzzing, banging, clicking, and humming
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A loud furnace often signals damaged or loose internal parts, with whistling pointing to airflow issues like a faulty blower motor or clogged filter.
Expect to pay $3,800 to $10,000 for a new gas furnace if your system reaches the end of its lifespan or needs a full replacement.
Rattling or banging noises from your furnace can indicate a cracked heat exchanger, which increases the risk of dangerous carbon monoxide leaks in your home.
Hiring a local furnace repair professional provides reliable support for diagnosing blower motors, heat exchangers, and ignition systems while keeping your home safe from gas hazards.
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Is your furnace screaming for help? There’s a certain amount of noise that furnaces normally make—like a light hum or a quiet rumbling. This may be slightly more pronounced in older models, but if your furnace is making loud noises, that’s a good sign there’s an issue. This guide will run through five of the most common repairs and the sounds to keep an ear out for.
Common Gas Furnace Problems
According to Angi data, nearly 41% of customers reported that their gas furnace or forced air heating system doesn’t provide heat or doesn’t get hot enough. Other common furnace problems include pilot light out, smells funny, makes odd noises, and cycles off too rapidly or runs constantly.
1. Faulty Blower Motor
If your furnace is making a whistling noise, that usually points to an issue with airflow—specifically the blower. Sometimes it means the blower isn’t getting enough air, whether it’s from a dirty air filter or blocked heating vents. Other times, it points to a problem with the blower motor.
A blower motor can wear out over time, or the bearings can overheat, causing the squealing. It could also rattle if the mount breaks.
How to Fix It
Check your vents to make sure they’re not blocked or closed. Change the filter if it’s dirty. If that doesn’t stop the squealing, lubricating the bearings can help reduce friction and get rid of the noise—but if the bearings are significantly worn, you’ll need to call a pro who can repair your furnace.
2. Loose Parts
Loose parts are one of the most common causes of a furnace making loud noises. If this is the case, you’ll probably hear your furnace making a rattling or clanking noise. Though this issue can occur with almost any component as it wears over time, the most common culprits are:
Fan belts
Panels
Ductwork
Blower wheels
How to Fix It
If you listen, you may be able to pinpoint where the noise is coming from. Check the nearby components for damage or loose fasteners. Tighten loose screws and lubricate the moving parts (the latter will solve any squealing due to friction). If components are damaged, you may need to replace them.
3. Faulty Heat Exchanger
Beyond loose parts, a rattling noise can also point to a faulty heat exchanger. This essential part of your HVAC system transfers the heat created by burning fuel to the air that heats your home using metal coils. Dirty components can stress the heat exchanger, leading to cracks. You’ll hear the noise as soon as the furnace turns on.
How to Fix It
A faulty heat exchanger is serious, because it increases the risk of a carbon monoxide leak. If you hear rattling, you’ll need to repair your furnace ASAP.
4. Problems with Ignition
If there’s a problem with your ignition, you’ll hear your furnace making clicking noises as the system struggles to light and start the combustion process. When this process is delayed, a small amount of unburned flammable gas will stay in the combustion chamber. When it eventually lights, you may hear your furnace making a banging noise.
Ignition problems have a number of potential causes. It could be due to:
Problems with your pilot light
Dirty burners
A broken sensor
A faulty valve
A burner malfunction
Low gas pressure
A defective ignitor
A defective control board
How to Fix It
Bring in a pro to figure out the problem. Since this is a gas appliance, you shouldn’t work on the ignition yourself. It can be extremely dangerous.
That said, some banging noises are normal. You may hear banging if you have metal ducts, which will expand when warm air blows through them. In this case, you can insulate your ducts to stop the noise.
5. Failing Electrical Components
If your furnace is making a buzzing noise or a loudly humming, it may have some electrical issues. This is one of the first signs that a major electrical component in your furnace is failing, whether it’s the blower motor, capacitor, inducer motor, or transformer.
How to Fix It
Faulty or aging electrical components in your gas furnace pose a safety risk, so you should bring in a licensed pro for this repair.
When to Call a Pro
Most of the time, if your furnace is making abnormal sounds, you should call a local furnace repair pro. DIY repairs are especially dangerous when working on a gas appliance because of the risk of a carbon monoxide leak or explosion. Furnaces, in particular, involve complex components, electrical systems, and combustion processes that require specific expertise to handle safely and effectively.
Although a pro can usually repair a certain component, you may want to consider a full replacement if your furnace is at the end of its lifespan or is an older, inefficient model. A new gas furnace costs $3,800 to $10,000 depending on the specific unit.
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