Funny HVAC Noises: What Do They Mean?

When I was a kid, I distinctly remember our old furnace making horrible creaking and groaning noises throughout the winter, not to mention the roar of the heat kicking on and the pilot flaring to life. It used to scare the bejesus out of me and my siblings. However, some noises coming from your HVAC system are perfectly normal, and are no cause for concern.


There are going to be instances, though, when the sounds coming from your furnace, air conditioning unit, or vents are indicative of something gone wrong. How can you tell the difference between a normal sound and a noise that heralds serious expense if you don’t rectify it immediately? Here are a few funny HVAC noises you might hear and what they mean for your home and your wallet.


Generally speaking, it’s perfectly normal for your HVAC system to make a humming noise when it’s running. This could be your furnace or AC unit hard at work, heating or cooling your home, or it could be the rush of air through vents and into living spaces. Unless the noise is getting noticeably louder, you probably have nothing to worry about. However, if you’re concerned you could always call your HVAC service provider to come and check it out.


When you want to hiss, you close your mouth and push air through the narrow space between your teeth to create the desired effect. The same basic principle applies to hissing sounds coming from your HVAC system. When you hear a hiss, air is probably escaping from somewhere it shouldn’t.

If you’re hearing hissing in the walls, don’t worry – no one opened the chamber of secrets and let a basilisk run loose. It’s much more likely that something in the ductwork has come loose along a seam and air is escaping into the cavity between walls. Just make sure the hiss isn’t coming from vents. If this is the case, adjusting the damper could just do the trick. If your ducts are loose, you’ll need the services of a professional HVAC technician to address the issue.


There are two likely reasons why your HVAC equipment might be making a rattling noise. Chances are there’s either a loose panel somewhere or something has gotten into your system and caused an obstruction. Either way, it’s probably best to schedule AC or heating services from Bradley Mechanical to come out and check, clean your system, and make any necessary repairs. If you leave twigs or other obstructions rattling around inside your system, there’s a good chance they’ll lead to damage.

Banging or Clanking

These are the noises you never want to hear coming from your HVAC system since they usually mean an important component has come loose. Even if you schedule regular furnace and air conditioner maintenance each year, your equipment will eventually suffer enough wear and tear that things are likely to break down. When this happens, you’ll hear banging or clanking noises that warn you something is really wrong. If this occurs, shut down your system and call for immediate help from your HVAC service provider.

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