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6 Strange Noises Your Furnace Should Never Make

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Furnaces often make noises as they run. They may hum or softly rumble, maybe even occasionally pop. These are all signs that your furnace is working perfectly fine. However, when you start to hear noises that sound a bit out of the ordinary is when you should become concerned. While a strange noise once in a while is no big deal, repetitive and abnormal sounds shouldn’t be ignored. 

If you are worried about a noise your furnace is making, don’t waste time searching for “heating and ac companies near me.” Instead, give our Cardinal Plumbing, Heating and Air team a call at 703-721-8888.

Need to learn more, first? Continue reading for six strange noises that your furnace should never make. 


A scraping noise coming from your furnace indicates that there is a major problem. This is especially true of metal against metal scraping. Typically blower wheel problems cause scraping noises. The issue may also be a loose internal part that is scraping against other parts of the furnace. 

No matter what the problem is, you need to call a technician right away if you begin to hear a scraping noise. A broken blower wheel or loose part can all negatively impact the efficiency and function of your furnace. In some cases, your furnace may even cease working altogether. Be sure to schedule HVAC repair as soon as possible. 


While it may sound like the popping noise is coming from the furnace, listen closely – does it sound like it could be coming from the ducts instead? A popping sound coming from ductwork is common, however not if it is in excess. These noises are happening because your air ducts are expanding and contracting from the heat that your furnace is giving out. 

A pop when your furnace first turns on is nothing to be concerned about. But, if you begin to notice popping noises over and over again, it could be a sign that your ducts need some work. The easiest way that this problem is taken care of is through insulation and sealing. Proper air duct sealing and insulation can make a big difference in the way your ducts function. Give your heating and air technician a call for ductwork repair and maintenance when you start to hear a popping noise. 


A banging furnace should be cause for concern. Even if you only hear it once or twice after you turn it on, there is an underlying issue that needs to be alleviated straightaway. Typically when a furnace begins to bang, it’s due to a burner issue. The burners on a furnace become dirty over time as they are used. Although this is completely normal, burners do need to be cleaned every once in a while. If they aren’t cleaned then your furnace will struggle to ignite and begin to heat your home. 

Banging happens when the burner cannot ignite right away, causing the gas to build up. When it finally ignites, it will cause a small explosion and a loud banging noise. This can become dangerous and may pose a fire hazard. It’s important that you schedule HVAC maintenance so that the burners are cleaned and any other issues are addressed. 


When you start to hear your furnace make a squealing noise, it could mean a number of things. The most probable cause for a squealing noise coming from your furnace is your blower. Specifically, a damaged or slipped blower belt can cause these noises. This is because the blower will try to run without having a smooth circulatory motion. The squealing noise will occur each time the blower belt goes around while damaged. 

Damaged blower motors can also cause squealing coming from your furnace. Either way, the best way to take care of this issue is to call a furnace technician to replace the blower belt. 


A rattling noise coming from your furnace is extremely dangerous. This usually means that your heat exchanger is cracked. A heat exchanger works to move heat from the combustion chamber to the blower. Inside of the heat exchanger are byproducts from the combustion chamber such as carbon monoxide. If the part becomes cracked, it can begin to leak this deadly gas. 

The rattling noise will come from the heat exchanger becoming overworked. It may rattle as it works harder to move the heat. If you believe your heat exchanger is cracked, call for emergency furnace service right away. You may also want to install a carbon monoxide detector over your furnace so that you can become alerted to the situation before it poses a threat to you and your family.


While hissing noises are not incredibly serious, they do indicate that there are underlying issues with your furnace. A hissing noise typically means that the flow of air is being constrained. This could mean that it is escaping through a small hole or tear. It could also mean that the air is not able to exit properly due to a blockage. 

If you hear a hissing noise, check to make sure that your furnace and vents are not being blocked by any objects or debris. In the case that it isn’t, you’ll need to call a furnace expert to check the situation out. The issue may also be an air duct leak or air filter blockage. A licensed professional will be able to tell you exactly what the issue is. 

Heating and AC Services Near Me

Abnormal noises coming from your furnace can be scary. Before you search “heating and AC service near me”, contact Cardinal Plumbing, Heating and Air. Our highly trained and qualified team is always ready to help. From cracked heat exchangers to slipped blower belts, we have seen it all. At Cardinal, we also provide services for air conditioners and plumbing systems. Choose our team for all of your HVAC and plumbing maintenance, replacement and repair needs. 

To schedule an appointment today, call our team at 703-721-8888 or book an appointment online


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