Understanding What Common HVAC Noises Mean

Most of us turn on the A/C before summer officially arrives. There’s something about the sound of cool air flowing through the vents that is calming. But, it’s definitely not calming when you begin to hear strange noises coming from your HVAC system. When it comes to HVAC noises, some are normal and some may indicate larger system issues you need to address sooner than later. We’ve compiled a common list of noises to help you determine if there are issues with your HVAC unit.


HVAC experts consider bubbling as the most alarming noise your unit can make. Typically, this noise occurs when the air is trapped in the refrigerant line, which may result from a refrigerant leak. Call Alps immediately to identify the issue and the location of the leak.


Clanking, which is commonly known as the sound of metal scraping metal, is usually a sign of loose parts. This may include fan blades that are not properly aligned or the loose pipes scraping other system parts. Avoid causing additional damage to your unit by having an Alps technician diagnose the issue.


Just like it sounds, hissing noises result when air escapes. A hissing noise that stems from inside your walls may be a sign of leaky air ducts. This noise may also result from simple issues such as a filter that is not properly sealed or vent flaps that are closed too tight. If you’re unsure what’s causing the noise, it’s a safe bet to call in the professionals.


Because metal expands and contracts during temperature changes, popping can be a normal noise you hear coming from your unit. You may also notice this noise if your ducts pop open or bang shut. Reduce the noise by installing additional insulation.


It’s not uncommon for small debris such as pebbles or twigs to slip through the grate protecting your outdoor condenser. Simply remove the vent cover to ride the condenser grate of small debris. If you’re unsure of what you’re doing, it’s best to call Alps to prevent the occurrence of additional damage to the unit.

Squeaking or Thumping

Our technicians often spot squeaking or thumping noises when a customer’s system starts up or shuts. This noise is typically indicative or worn belts. Consider scheduling a routine maintenance appointment with Alps to prevent worn parts from breaking.

Have a question about a noise your system is making? Ask it here and we will get back to you with the answer.