Laughter, music …those are good noises you want to hear in your home. Then there are other noises you don’t want to hear, like banging and squealing from your HVAC system, as they can indicate a bigger problem. To help you understand the noises, here are six you don’t want to hear coming from your HVAC system and what they might mean.

What Noises are Normal?

Noisy systems are no good, but neither are silent ones. So is there a certain amount of noise that’s normal and good to hear? Yes, there is.

What you want to be hearing from your system is the “whoosh” of airflow from your vents into your home. That lets you know your system is doing its job. Aside from this, other sounds that are normal to hear include hearing the motor running or humming.

Noises You Shouldn’t Hear from Your HVAC System

Noticing other sounds from your HVAC system? Let’s go over what some popular sounds could mean for your system.


If you’re hearing a squealing sound coming from your HVAC system, it usually means something is wearing out and breaking. For example, the belt may be wearing out and need replacing. Or the motor bearings are damaged, which can cause the motor to be off-center.

If you notice this sound, hire an HVAC technician to come and fix the issue as soon as possible. That’s because, typically, the belt and motor bearings aren’t completely broken if you’re hearing squealing. If you catch the issue before they stop working altogether, then you’ll prevent your HVAC from shutting down. Regular maintenance will also help to catch these problems early and keep these parts in good shape.

Thumping or Banging

There could be a few reasons you’re hearing thumping or banging from your system, and the loudness of the thumps can help you figure out what problem you’re dealing with.

Thumping on the softer side can indicate your air filter is hitting the return grille (the piece that covers the duct and filter). If you’re experiencing this problem, tape your filter to the return grille to avoid more sounds. However, loud thumps or bangs could mean the blower fan has become loose or another part is becoming loose. If you notice the banging sounds have gotten louder, shut your system off and call in an HVAC expert. At this point, whatever was loose is likely broken or disconnected.


Unfortunately, your HVAC system shouldn’t whistle while it works. If it does, then something is blocking airflow in your ducts or supply vents. First, ensure your vents have enough space for them to do their job. That means they aren’t blocked by furniture, clothing, dust, or debris.

If you still notice whistling, the problem could be in your ducts. Blockages, punctures, and improper installations can block airflow, producing a whistling noise. Call in an expert to help you inspect your ducts and get to the bottom of the whistling problem.

Repeated Clicking

A clicking noise when your unit is starting up or turning off isn’t cause for alarm, but if you notice repeated clicking, that’s not typically a sound you want to hear coming from your unit. Repeated clicking could be caused by:

  • The relay process – repetitive clicking could indicate there’s a problem in the relay process in the thermostat.
  • An electrical problem – clicking can also mean there’s an electrical problem connected to the HVAC system.
  • The contractor – it could also indicate the connection between the thermostat and the compressor unit could be damaged and need replacing.

As your AC cools your home, moisture develops along the process. The moisture doesn’t hang around for long, as it goes into a condensate pan and quickly down a drain. Since the moisture is discarded quickly, you shouldn’t hear a dripping sound. If you do, it’s an indication that the condensate pan isn’t draining properly. Check the drain tube in the drip pan for any blockages preventing the water from flowing out. Remove the debris, and the dripping should stop.


A loud hissing noise coming from your system could mean there’s a refrigerant leak. If you hear a hissing noise, it’s important to take action immediately, as refrigerant is harmful to the environment. Don’t waste any time – shut down your unit and call for a professional right away. They’ll not only be able to refill the refrigerant but also find the source of the leak and repair it.

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Whether you’re looking for help with a noisy HVAC system or need someone to perform maintenance, Comfort World Air Conditioning & Heating is here for you!

How to Prevent a Noisy HVAC System

If you want to avoid these noises coming from your HVAC unit in the future, regular maintenance is the best way to do so. An HVAC technician will be able to detect minor issues before they before they become significant ones and mitigate problems entirely. Maintenance in the spring and fall will make sure that everything is working as it should and no odd noises pop up in the winter or summer.

Whether you’re looking for help with a noisy HVAC system or need someone to perform maintenance, Comfort World Air Conditioning & Heating is here for you! We will work quickly and efficiently to solve the problem so you stay comfortable. We’ve been bringing comfort to the valley for over 30 years, so you can count on us to get the job done right. Our highly trained technicians in Scottsdale, Arizona, want to bring a little more comfort to your world!