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Fire & Water - Cleanup & Restoration

Noisy HVAC? Here’s Why and How to Fix It

6/10/2022 (Permalink)

Woman covering her ears. Old HVAC systems make a lot of noise.

HVAC systems tend to make strange noises, but any homeowner can usually recognize when the sound changes into something different. Diagnosing where the sound is coming from is usually the first step to diagnosing the problem, but the type of noise itself can give you a major clue about the type of problem you’re dealing with. Here are 11 of the most common HVAC noises that you may encounter and how to handle them.

11 Common HVAC Noises and What They Mean


Something is loose or broken. Typically, this is either the furnace blower or the motor. Additionally, there could be debris inside the system. Check for loose screws. If the rattling gets louder as it runs, turn it off and get professional help because something is broken or disconnected.


Popping happens when warm air goes through cold ducts, but this should only happen when you haven’t used your heater in a while. Besides first turning on your system, you might hear popping noises if fluid is leaking or freezing.

Scraping or Thwapping

Typically, these scraping sounds are not indicative of monstrous issues, but a problem with the fans. Something is obstructing the fan blades from properly moving, which damages the blades, and the motor, and can even lead to a refrigerant leak.


Humming is caused by loose parts, electrical problems, or motor issues. While humming is not a dire problem itself, it’s often a harbinger of HVAC problems.


Clicking can happen for several reasons in an AC unit. It can be difficult to pinpoint the cause without the help of a technician. If your heater is clicking, it could mean there’s a problem with the ignition system.


A boom is often preceded by clicking. Your furnace will make a booming noise when it tries to light but doesn’t work. It will continue its attempts, creating a build-up of gas that lights up all at once when it finally ignites. A technician should take a look at it, but you may also need to have the flue and chamber inspected or cleaned.


If the hissing is coming from your AC, it’s usually due to an internal refrigerant leak in the compressor. Turn off the power to the AC immediately and get it checked. If your furnace is the source of the hissing, there’s likely a leak in the furnace itself or in a connected air duct that needs to be replaced.


There are four main reasons why your HVAC is buzzing: the compressor is malfunctioning, the refrigerant may be leaking and freezing the parts, debris is blocking regular movement, or there’s a loose part that’s shaking. If the buzz comes from your AC, you might need to clean the condenser coil or change the air filter. Regardless, you’ll want to get it looked at.

Clanking or Banging

Banging or clanking is similar to rattling and usually comes from a loose part of your system. You may need to replace the compressor, realign the fan blades, or balance the indoor blower if the noise is coming from your AC. A boiler will bang if scale forms on the heat exchanger as well.

Screeching or Squealing

A loud screech is typically the fault of a bad fan belt that needs to be replaced. However, it could also be caused by a malfunctioning motor or blower. Your motor could need lubricant, but if that doesn’t help, a technician will be able to determine the problem.

Whistling or Screaming

High-pitched whistling or screams are not a good sign. When the noise comes from a boiler, the air is likely trapped in the system. If your AC is the culprit, turn it off right away. There could be a leak that’s building into a high refrigerant pressure. Don’t turn it on again until you can have a professional look at it to determine the problem.

We Hear You: Calling in the Professionals

When you have a strange noise coming from your HVAC system, don’t panic. Follow these guides and contact a professional HVAC service to help you resolve the problem and the noise behind it.

To help prevent these unsettling noises and the even more frightening issues causing them, you should get your HVAC system checked once a year. If you have a heat pump that’s doing double-duty heating and cooling, you should schedule an appointment every 6 months. Regular tune-ups and inspections can save you lots of money—and frustration—down the road.

If your HVAC system is making any of these noises, contact the technicians at SERVPRO of Cedar City/Fillmore. We’ll diagnose the problem and, even better, fix it for you so that you can rest at ease again. Contact us today to schedule an appointment or to learn more about our services!

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