What Do Those Funny HVAC Noises Mean?

Colorado is known for its changing weather. Even in the heart of the summer, temperatures can fall 20, 30, even 40 degrees or more in a single day. And with a cold front in place, it may be days before you need to turn your air conditioning system on once again.

When you do, the only sound you hope to hear is a gentle whoosh as it kicks in and starts cooling off your rooms. But from time to time, you may hear other noises that have you wondering if your HVAC system is in need or repair.

Some are serious. Some indicate problems. Some can be common sounds that will easily go away. Here’s a sampling of what you might hear.

A Bigger HVAC System Isn’t Always The Best ChoiceRattling

Sometimes the fan can blow around something loose, causing a rattling sound somewhere deep in your system. The question is where. Your outdoor condenser is protected by a grate that keeps out large debris, but occasionally small things can slip through. Small things can also find their way into your system through indoor vents, especially if they are installed in the floor. You can usually retrieve these yourself by removing the vent cover and pulling the item out. If you can’t find it or doubt removing an outside grate, you can call in a professional.


Squeaking usually begins when belts begin to decline. These components are thoroughly checked during any tune-up on the equipment, so consider scheduling one at the beginning of each season before the equipment is put into use.


A metal on metal sound can be caused by loose parts, such as a fan blade that has fallen out of alignment. It could also mean a loose pipe is clanking against other parts. Any movement can continue to cause damage internally in the system. The sooner you repair it, the better.


If a loud hissing noise is prominent, it could mean air is escaping where it shouldn’t If it’s coming from inside your walls, it could be leaky ductwork. If it’s coming from the vents, you might have flaps that are closed too tightly. If you hear it coming from the furnace, the filter may not have an adequate seal.


A bubbling noise often indicates air is trapped in the refrigerant line. You may also have a refrigerant leak. Call an HVAC technician right away as it can cause internal problems with your HVAC equipment.

Have additional questions? Give us a call today.

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