Why is My Air Conditioner Making Noises?

April 6, 2021
Man working on air conditioner

Many people turn a deaf ear to noises their air conditioners make. Part of this avoidance is fear of the hassle and cost of replacing the system. Fortunately, not all noises indicate a catastrophic system failure. However, if left unattended, strange noises could lead to that unfortunate fate.

While you may never be an air conditioner whisperer, you can learn to tell what various noises mean. With that knowledge, you can then know when it is time to call in a professional.

Constant or Repeated Clicking

When you listen to your system, you may notice a series of normal clicks from various parts of the unit. These may include your thermostat, the contactor in your condensing unit, and a series of relays. However, they should click as the system initializes and be done.

If the clicking continues or repeats regularly throughout the cooling cycle, it indicates a problem. A common one we see is the contactor failing to initialize properly. When this happens, it continues to signal the compressor to turn on and off. This rapid cycling will put unusual strain on the compressor, reducing its service life.


Rattling is a regular sound from any HVAC system. It is caused by parts that loosen due to the vibration of the system running. However, loose parts left unchecked can cause strain and damage to your appliance.

Rattling can also be an indication of debris caught in the system, especially in one of the fan assemblies. For sounds coming from outside, check to make sure there are no twigs caught in the condensing fan assembly.

Your seasonal maintenance appointment should include checking the normal culprits for vibrational loosening. Your technician will also inspect the blower motor, clean it, and ensure there is no debris in the assembly.


Squealing can be difficult to trace because it is easily transmitted through your ductwork. However, it commonly comes from one of the two fan motors in your system. When these motors are going bad, they will emit a loud squeal or squeaking sound.

Some units will make this sound briefly as they start up, which is normal. If you notice a new squeal or one that is constant throughout the cycle, contact a professional for a diagnosis.


Screaming from your air conditioner can raise the hair on the back of your neck, as well it should. This kind of sound indicates a refrigerant leak somewhere in your unit. Shut down your system immediately, and then wait to start it until a repair technician has inspected the appliance.

Running your air conditioner without enough refrigerant will damage the compressor, leading to expensive repairs. If the leak is inside, the refrigerant is also dangerous to the people inside your home. Consider cracking your windows if you suspect an indoor refrigerant leak.

Buzzes or Hums

Humming and buzzing may be faint or very loud. Some systems may have a very faint humming as they initialize. However, in most cases, this is a sign that something is not working properly.

The first concern for this kind of sound is an electrical component failing. Of specific concern outside is the capacitor in the condensing unit. This stores a large charge to kick start the compressor motor and condensing fan.

These sounds can also be caused by loose parts, debris caught in the system, or even a clogged air filter. If your filters are clean and you are confident there is no other debris in the system, call an AC technician to investigate the cause.

Whirring Like a Helicopter

Sometimes, your unit may emit a sound similar to the whirring of a helicopter rotor. The most common cause for this is loose fan blades or an off-balance fan. It could also indicate the bearings in your fan motor are wearing, needing a motor replacement. If the sound seems to be buried deep, it could be as simple as a piece of paper caught in one of the fan assemblies.

When you ignore what seems like a faint sound at first, it inevitably turns into a larger problem. Keep your repair bills down by turning to an air conditioning technician at the first sign of a problem. People throughout Greenville have trusted Ken Parker Service, Inc. for air conditioning repairs and maintenance for more than 40 years. Our technicians are also indoor air quality and heating system experts. Call us today to have one of our expert technicians come to track down the source of your AC noise.

company icon