5 Sounds Your HVAC System Should Never Make

Posted on Sep 3 2021 - 9:21am by Housecall
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By Anita Ginsburg

You probably recognize the typical low, blowing sounds your HVAC system makes. However, sometimes, it can make irregular sounds. When it makes a sound you haven't heard before or that doesn't seem quite right, you may choose to ignore it, perhaps thinking it will eventually go away. But this could be a big mistake. There are at least five kinds of sounds your heating and air conditioning system could make that indicate serious problems that you must not ignore:


The most common reason for rattling is a loose nut, bolt or piece of wiring. It could also mean a buildup of twigs, leaves or other debris in the outside unit. However, it could be a more serious problem. For example, the motor bearings might be going out. If you can't find the problem yourself after a quick examination, it's time to call for professional diagnosis and service.


You should call an air conditioning maintenance company right away if you hear a banging noise coming from any component of your HVAC system. The most common cause of banging is a bent fan blade, but this type of sound could also indicate an expensive compressor problem. In all cases of banging, professional air conditioning maintenance is required. You should turn the system off until help arrives to prevent further damage.


If you hear whistling or hissing that you haven't heard before, this probably means you have a leak in your system. The worst-case scenario is a refrigerant leak, which is dangerous to the health of everyone in the home. This type of sound could also mean your heat pump is leaking air or that your ductwork is damaged. These are less serious problems than a refrigerant leak. However, they still need to be fixed for the system to operate efficiently.

Clicking or Buzzing

Clicking, buzzing or unusual mechanical hums often indicate electrical problems. Continuous clicking could mean a relay needs to be replaced, while buzzing or humming may indicate problems with electrical connections or circuit breakers. If you're not experienced working with electricity, you should not attempt to fix these problems yourself.

Screeching or Squealing

Just as with an automobile engine, screeching or squealing usually indicates a problem with a belt or bearing. When an HVAC system motor goes bad, this sound is often the first sign. If you're lucky, this type of high-pitched noise could simply mean the system needs lubricating, especially if you only hear the sound when the motor turns on or off.

A quick diagnosis and repairs are essential when you hear any unusual sounds coming from your heating and air conditioning system. The problem is unlikely to get better on its own, so it’s important to get regular air conditioning maintenance done by a professional when you notice problems. The longer you allow it to persist, the more expensive and difficult it may be to repair.

Anita Ginsburg is a freelance writer from Denver, Colorado. She studied at Colorado State University and now enjoys writing about health, business, and family. A mother of two wonderful children, she loves traveling with her family whenever she isn’t writing. If you notice problems with your HVAC system, she recommends getting air conditioning maintenance. You can find her on Twitter @anitaginsburg.