Your air conditioner making noise makes up the soundtrack of your spring and summer home life. Any change in air conditioner noises can quickly cause alarm. At Poston Brothers, we receive calls and inquiries about every type of air conditioning noise. Some sounds have simple solutions while others are warning signs to shut down your air conditioner immediately. When you understand the common types of air conditioner noises, you can react quickly to protect your HVAC system.

What Do Air Conditioner Noises Mean?

A sudden change in AC noise is not always cause for alarm, but you should react appropriately. Before you try to diagnose an air conditioner repair based on sound alone, you should understand that the key advice anytime you encounter changes in AC noises is to contact a professional HVAC expert. Certified technicians help to accurately diagnose the issue and quickly perform the necessary repairs. The second key point is calling on an HVAC tech as soon as you notice a problem. Many expensive repairs and in extreme cases replacement of air conditioners could have been avoided. The longer a symptom is ignored, the more extensive the damage.

A clicking noise, buzzing sound or rattling noise from your outdoor unit can indicate a number of issues. Your cooling system has many moving parts so a loose hardware connection can create rattling noises that are simple repairs. That same type of noise can also indicate a bearing or seal is damaged. While this comprehensive list of air conditioner noises and what they could mean is helpful, only a trained and skilled tech should diagnose and repair your air conditioner.

Common Air Conditioner Noises


One of the most frequent sounds is squealing from the outdoor unit or the interior air handler. If your air conditioner is making a high pitched squealing noise, it usually indicates a fast moving component.


A few of the components that may be squealing from your air conditioner are the drive belts. Some AC units use belts to operate the blower fan or other components. The belt moves quickly during operation around a pulley. As the belt wears it may become misaligned. Bearings within the pulley and other moving parts can also fail and begin to squeal. If you notice an issue with the belt, a simple replacement may prevent more expensive repairs and damage to more costly components.

Blower motor

Bearings and other small parts can fail within the blower motor. If this happens, you may hear a squeal or shrieking noise. The motor moves quickly and the noise is typically high pitched and stops when the fan is off. The blower motor is responsible for circulating air through your AC system. If the motor is worn or damaged, you may also notice a weak airflow.


Issues with your AC unit fan can also cause squealing sounds. The fan helps to circulate air throughout the system. Dirt on the fan blades and damage to the fan can cause imbalance and squealing. Another symptom of fan issues is banging sounds. If a part becomes dislodged in the housing the fan will reverberate throughout your duct work.


Lack of lubrication on parts and loose parts can also squeal and squeak. The various components in your AC system require lubrication to operate smoothly. If they become dry, it can cause a squealing noise. Routine maintenance prevents this issue.

Humming sounds

Another frequent cause of sounds from your HVAC system is humming noises. These may be caused by electrical issues or airflow.

Loose wires and connections

Vibrations from high speed components may cause hardware and other parts to become loose over time. A stripped wire, bad electrical connection or even corroded connections can cause a humming sound within an AC unit.

Clogged air filter

The sound will not come from the air filter. Rather, a clogged air filter can cause the AC unit’s fan motor to work harder than it should. Under strain, the fan motor may emit a humming noise.

Low refrigerant

Like an air filter, the humming will not come from your refrigerant or the refrigerant lines, but typically causes the compressor to work harder. In extreme cases, a breakdown of the air conditioner will occur. Another symptom of low refrigerant levels and leaks is warm air blowing out of your vents.


The capacitor engages the outside AC unit’s compressor and fan motor. A faulty capacitor may hum or buzz when failing. Humming and buzzing noises are very similar but may have unique causes.

Buzzing sounds

A steady buzz from your air conditioner may be due to lack of maintenance. Air conditioning maintenance is the best way to prevent air conditioning repairs. Many noises are preventable issues caught during annual inspections and cared for during regular tune ups. Buzzing noises from your air conditioner can be unexpected, though. A sudden electrical shock or surge can impact your unit.

Fan motor

Age and neglect can catch up with the fan motor. As one of the primary components within the system, a faulty fan motor will buzz incessantly and may even reduce the airflow throughout your home. This is definitely a component you want to care for. If you experience any power changes or strange noises from your fan motor, turn off the system and call for professional help.

Coil issues

The coils in your AC unit can become dirty or damaged over time. This causes the system to work harder than it should, which can produce a buzzing sound. These components are cleaned and inspected during maintenance to avoid these issues. Another indication of dirty coils is sudden increases in your electric bill.

Bubbling sounds

A bubbling sound may occur when a refrigerant leak is present. Refrigerant is under high internal pressure. A crack in coils or damaged refrigerant lines may present as a bubbling noise. Another liquid sound is gurgling. Condensate lines can become clogged or overflow. If you hear a bubbling or gurgling check the pan and lines for blockages.

Loud noises

There are some sounds that are clear warning signs that you should shut down your system. Whether from the outdoor unit or indoor unit, loud sounds, vibrations and metal against metal can be dangerous and seriously damage your air conditioner and HVAC system. Promptly turn off your system and call for professional air conditioner repair if you experience any of the following strange sounds:

  • Banging sounds
  • Grinding noises
  • Pulsating noises
  • Hissing sounds
  • Whistling noises

What are the Primary Warning Signs of an Air Conditioner Repair?

Timely repairs help to ensure your AC is running and peak efficiency. Some noises are the last warning cries of a breakdown. There are several other warning signs to be alert for prior to hearing any noises.

  1. Reduced airflow: If you notice that the air coming out of your AC vents is weak, your ducts may be damaged, your blower motor may be damaged or your unit could be straining.
  2. Warm air: Warm or hot air blowing from your vents is a clear problem. Obviously you will need to check to make sure the thermostat did not switch from the cooling cycle to heat. The issue may not be in your AC unit but rather a malfunctioning thermostat or just a clogged air filter. You will still want to get to the cause quickly to avoid the shock of AC noises.
  3. Major increases in bills: A sudden spike in energy use is always a concern. When something is wrong with your AC unit, the system will use more electricity to cool your home. Checking your bills is a wise decision.

What to do if Your Air Conditioner Needs Repairs

If you experience any issues with your air conditioning the best practice is to turn off your system and contact a professional. From a loud banging noise to a low whistling sound, you should not risk further damage to your air conditioner. There are items you can check once you turn off your system. Air filters clogged with dirt and airborne debris will cause parts within the air handler to work harder. In the outdoor unit you can check for any foreign objects, dirt build up on the fan and loose hardware. Otherwise, trust an AC technician to diagnose and repair your HVAC unit.

What to Expect When an HVAC Professional Repairs Your Equipment

Certified technicians have the training and tools to test your central AC and provide a clear option for repair. You should expect the appointment to take some time. Highly skilled technicians and reputable contractors evaluate the overall condition of your equipment before providing advice. If the cause of a squealing sound is just an issue with fan blades or a worn belt, then a repair will always make sense. In some cases where a faulty motor or faulty outdoor condenser unit is the cause of loud noises, than the age and overall health of the air conditioning system should be considered.

How Poston Brothers Provides AC Repairs

In the case of Poston Brothers, our team provides a clear and an easy-to-understand diagnosis. As a local company, our reputation is key to our success. This means we answer your questions and allow you to make a thoughtful choice about how to fix AC noises. Our team never puts pressure on customers because we know losing your cooling system can be stressful. We allow you to make the best choice for your family, home and budget.

Once the repair is complete, our technicians test your entire system. As any quality local HVAC contractor should do, we stand behind our work and quickly respond if any other issues arise with your system.