AC Noises: Which Signs Point To Repair

A noisy air-conditioner could quickly turn a calm environment into a stressful one. Hearing your air conditioner make loud noises can be unpleasant, but it can warn you of possible issues. A noisy AC is most certainly having a malfunction or a problem that requires immediate attention.

Is humming normal?

A faint hum is normal and usually isn’t a reason to worry. Humming is fairly common with older systems, and most air-conditioners make some noise as they complete a cycle. However, deafening noises may indicate that your AC is in desperate need of repair.

10 noises that might mean problems with your AC

Here’s a thorough list of AC noises to help you troubleshoot potential problems:


When the pressure within your air conditioner becomes too high, it may produce a screeching sound. If you hear a loud screech, the most probable causes are worn-out belt or blower fan motor bearings. There may also be a malfunction with the compressor or the fan’s motor.


Be careful if the hissing starts as soon as the air conditioner is switched on. High pressure in the compressor could be the cause and is quite dangerous. If your AC has a refrigerant leak, it may create a hissing sound and result in inefficient cooling. If the air conditioner is still running, turn it off immediately and call a technician.

Hammering sounds

Several issues can cause hammering noises from your air conditioner. An out-of-balance indoor blower might cause cyclic booms or bangs. If that isn’t the case, the compressor’s hammering sound might be due to a damaged compressor or loose connecting rod, piston pin, or crankshaft.


Metallic clanking could occur if the interior and external fans are not correctly fastened. An out-of-balance or faulty unit might cause a noisy compressor. If that is the case, you may need a new compressor.

Whistling sounds

To eliminate whistling noises from the cooling system, clean or replace the air filters. Clogged air filters often result in whistling noises, but your HVAC ducts might also be at fault. In some cases, the ducts may be too small, or the ductwork might be leaking or damaged. It may also be the result of a refrigerant leak, which must be repaired by an expert.


The gurgling sounds produced by an air conditioner are similar to bubbling liquid. Condensate going down the drain line or a refrigerant leak might also cause gurgling. Switch off your system if you are confident in your ability to fix the problem. Otherwise, it would be best to call a technician.


Consistent loud buzzing from your air conditioner is often the result of an electrical fault with the condenser fan motor, relay switch, or wiring. Electrical issues may be dangerous and should not be overlooked. If you suspect an electrical problem with your unit, turn it off and call a professional.

Rattling noises

Rattling noises may be caused by pebbles or twigs caught in the air conditioner’s external unit. Screws, nuts, fan blades, and cover plates may also loosen with time and cause similar issues.


It is normal to hear clicking sounds when your air conditioner starts or stops. But if the electrical components are continually clicking, this is usually a sign of a problem. In such cases, you may need to have the thermostat or the air conditioner’s controls repaired or replaced.


These may be the least alarming noises produced by air conditioners. Most units have a faint humming sound when running, which is usually normal.

On the other hand, a loud humming sound could indicate a problem with the fan. In some cases, a thorough cleaning will fix the issue. But if worn-out components, bent fan blades, or a malfunctioning fan motor is at fault, they will have to be repaired or replaced immediately.

If your air conditioner is making any of these noises, don’t ignore it! These sounds might indicate a serious problem that could worsen over time. Having your system checked could prevent costly repairs.

J.A. Bertsch

J.A. Bertsch Heating & Cooling offers professional residential air conditioning services throughout Kootenai County. Our licensed A/C technicians cover all of North Idaho and our neighboring cities. Experience superior, award-winning service 24/7. Call us at 208-715-9694 to schedule an appointment.

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