Overtime, we tend to get used to the various noises around our house. In fact, these noises can even become a comforting symbol of the familiar. However, there are some noises that you should not get too comfortable hearing, especially if they are coming from your HVAC system. To help you become a pro at identifying some not-so-routine noises, the team at Freedom Air and Heat is here to share 4 sounds your AC unit should not make.


Banging or Clanking

If your AC unit is making a banging or clanking noise, it can be an indicator of a loose or broken part. Considering all the different parts of a unit, this could be a loose connecting rod, piston pin, or crankshaft. Another reason for this sound could be an unbalanced indoor blower or damaged compressor that must be replaced.



A buzzing noise from your unit could mean many different things, from loose parts to refrigerant leaks. Here are some possible causes to investigate:

  • Loose parts
  • Debris in the indoor or outdoor unit
  • Loose or unbalanced fan blades
  • Dirty condenser coils
  • Air filters that need to be changed
  • A damaged or unbalanced blower
  • Refrigerant leaks (if you also notice that your AC unit is not cooling, this could be the issue.)




For squealing noises coming from your AC unit, you should investigate your motors. This means checking your outdoor fan motors and indoor blower motors for signs of damage. When inspecting your indoor blower, ensure the wheel and housing are not damaged or out of balance. While sometimes this can be a normal “start-up” noise, you can reach a definitive conclusion about the severity of this noise after a professional inspection.




Perhaps the most alarming AC sound is screaming. If you hear high-pitched whistling or screaming coming from your AC unit, you should shut off your air immediately and call a professional for an emergency home visit. The reason for the recommended urgency in this case is due to the cause most likely being a refrigerant leak. In any instance, a refrigerant leak can damage your AC unit and pose serious threats to your family’s health. Another dangerous cause for this noise could be high internal pressure within your compressor. If your sensors are doing their job, your AC should shut off in this case, but it is still a good idea to have a professional perform an inspection asap.


More Sounds Your AC Unit Should Not Make

While the previously mentioned noises are the most common, there are more AC noises to be wary of:


  • Repeated Clicking Sounds

Although an initial clicking sound can be a routine noise when your AC starts up or shuts down, continuous clicking is a different matter. Here are some possible causes:


1. A Loose Object in Your Blower Fan 

This sound could mean there is a loose object nestled in your blower fan that is hitting against the fan as it spins.


2. An Issue with Your Control or Thermostat 

Another cause of this sound could be a defective control or broken thermostat.


3. A Defective Relay 

If you hear repeated clicking sounds from the control panel or outdoor compressor, you may have a defective relay.



  • Rattling Sounds

Another sound that you should not hear from your AC unit is rattling. Especially if you hear this noise from your outside compressor and fan unit, it could indicate loose hardware or a failed motor. The louder the sound, the more serious the problem might be.



  • “Thwapping” Sounds

Like the noise that comes from playing cards attached to bicycle tire spokes, this sound could mean a few different things. If your blower motor makes a fast “thwapping” sound when it runs, it could indicate something may be stuck in the blower blades. Also, there may be something inside the housing hitting the blower while it turns. Although this noise does not always require immediate attention, you should still consider having a professional look at it. Because it may mean a loose object inside your unit is creating resistance, your motor could wear out abnormally fast. In any case, it’s always better to be safe rather than sorry.


  • Hissing Sounds

Last on our list of sounds your AC unit should not make is a hissing sound. Although this is fairly normal for furnaces, a hissing sound from your AC unit could indicate a few possible problems. Some of these include a duct leak, ill-fitting air filters, or a faulty expansion valve. However, it is most likely a refrigerant leak, which warrants a visit from your local HVAC technician asap.


Looking for a Professional Opinion?

If you hear any of these 4 sounds your AC unit should not make, you will need a knowledgeable expert’s help. With years of HVAC experience under our belt, the team at Freedom Air and Heat has just the technicians for the job! For reliable service from one of our pros, call us today at 321-631-6886 or fill out a service request form on our website.