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Four Furnace Sounds You Should Never Ignore

When it’s time to warm up, sometimes turning on your furnace is accompanied by noises that you don’t expect. While a heater might work while making strange noises, you shouldn’t ignore them for very long! A noisy furnace can be a sign that that something is seriously wrong with your unit. While some noises are harmless and expected, knowing which ones are a sign that you need to repair or replace your furnace can save your wallet as well as your safety!

Clanking & Scraping Sounds

If you hear a sound that resembles metal-on-metal noises, you should turn off your furnace immediately. Clanking, scraping, and rubbing noises could be a sign that your blower wheel is malfunctioning. Turning off your furnace can help prevent further damage from happening and ensure that repairing your blower wheel is a simple, fast, and affordable process. In the most severe instances, these noises could mean that the blower and motor have broken and a furnace might need an entire assembly.

Whistling Noises

If your furnace makes a whistling sound while on, it could be a problem with its gas valve. If this is the case, always leave fitting new gas valves to a professional who is trained to safely handle this type of work!

Loud Bangs, Rumbles, Knocks, or Booms

If turning on your furnace makes you jump with a loud bang, it’s time to turn it off immediately and call JD Service Now. Loud noises like this are a sign of a build of gas in a furnace. The noise you hear can mean your heat exchanger is at risk of cracking. Even worse, it’s a sign that something dangerous could happen if you continue to use your heater.

A loud bang could mean that a furnace can’t light correctly because of a dirty ignition or igniter. When this happens, each failed ignition allows more gas to collect within a furnace. When it finally lights, a small explosion can occur because of the buildup of gas.

Notably, subtle knocking and popping sounds aren’t a bad sign for furnaces. When a furnace is turned on, it can heat the cool metal of a home’s ducts. This is natural and isn’t something that is dangerous or a sign of a failing furnace. If you hear noises when turning on your furnace and are unsure if they’re acceptable, it’s always best to call our Durham HVAC pros to make sure you’re safe.


If it sounds like something metal is bouncing around your furnace while it’s on, it could be a sign of loose panels or screws. Checking for these can confirm if your furnace needs professional attention and if it’s safe to use. If you can’t locate the source of your furnace’s rattling, the noise might be a signal for a dangerous problem.

Leaks and cracks in a furnace heat exchange can produce rattling sounds. These are dangerous because they could introduce unsafe amounts of gas into a home. As a result, rattles that can’t be identified should always be handled by a trained HVAC professional from JD Service Now.

How to Prevent Your Furnace from Making Noise

One of the best ways to make sure a furnace won’t make unexpected noises or become dangerous to use is through regular maintenance. At JD Service Now, our team of Durham HVAC maintenance pros is ready to inspect your system, make sure it’s ready to run as it should, and identify any problems that could become unexpected issues in the future! Maintaining your furnace doesn’t just mean that it’ll work when you need it—it also helps make sure you and your loved ones are as safe as you are warm!

To learn more about our Durham, NC furnace maintenance, call us now at 919-383-7000.

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