Why Is My AC Making a Loud Noise?

There are a lot of different noises your air conditioner may be making. For each type of sound, there are many possible reasons. To determine what makes your AC so noisy, you need to listen to it carefully. You also should ask yourself when the noise occurs. 

There are a lot of different noises your air conditioner may be making. For each type of sound, there are many possible reasons. To determine what makes your AC so noisy, you need to listen to it carefully. You also should ask yourself when the noise occurs. 

Does it happen only during startup or shut-down? Is the volume loud or soft? These questions will help you and your contractor diagnose the problem.

Banging Sound

It is very rare for an AC to make a loud banging sound. But if it does, it is most likely from the compressor inside the outdoor unit. If your AC is old, it might be caused by wear and tear. The parts probably got loose and damaged. If this is the case, then you likely need to buy a new AC unit.

However, if your AC is relatively new and you start hearing a loud banging noise, it is most likely due to a build-up of ice inside the outdoor unit. This usually happens when the AC is not used for a long time or when it is used excessively. The ice build-up can damage the compressor and other parts of the AC. If this happens, you will need to repair or replace the AC.

If you hear a loud banging noise from your AC, turn it off immediately and call a professional for help. Do not try to fix it yourself as you might damage the AC further.

Clicking Sound

If your thermostat is running on “Fan Mode” while your outdoor unit is constantly clicking, it is probably your fan. An object might be stuck inside, or the blade might be loose. So first, look at your outdoor unit and see what your fan blade is hitting. 

If you can’t solve the problem, call a professional maintenance specialist. Another possibility is that your air conditioner’s compressor is failing. The compressor is the part of the AC unit that pressurizes the refrigerant and circulates it through the system. 

If it fails, it can cause a knocking sound. So again, this serious problem should be fixed by a professional as soon as possible. 

Hissing Sound

A hissing sound usually means something is leaking. It can either be your refrigerant or a leak in your air duct. Aside from the hissing noise, you may also feel that your AC is not cooling the room. This is because the cold air fails to make its way to your room.

There are a few things you can do to fix this. One is to check for any holes or cracks in your air duct. If there are any, seal them up with duct tape or something similar. Another option is to check your refrigerant levels and see if they need to be refilled. This can usually be done by a professional. Lastly, try insulating your air ducts to prevent the cold air from escaping.

Leaking occurs if you neglect the regular maintenance of your HVAC system. Therefore, if there is a leak in your HVAC system, it is essential to fix the problem quickly.

Screeching Sound

Screeching sounds commonly come from friction between two worn-out metal parts. Most of the time, just a bit of lubrication will solve this problem. Unfortunately, a screeching sound can also mean the motor has been damaged. If that is the case, lubrication will not help at all. You would need a total replacement.

Whistling Sound

A sound similar to water boiling in a kettle usually means an airflow problem in your HVAC system. First, you need to check the compatibility of your air ducts with the machine. If the duct is undersized, the airflow pressure may create a hissing sound when coming out of your vents. A leaking duct and clogged filters can also cause a whistling noise.

Rattling Sound

A rattling sound from an old appliance usually happens because of some loose parts. It can be as simple as a loose metal screw, but it can also mean your motor is starting to wear off. Ask for a licensed HVAC technician for a proper inspection.

Ideally, your AC should not make much noise at all. Its job is to make us feel more comfortable inside the room. Loud noises contradict that goal. By noticing and identifying the type of noise, you can determine the real culprit and solve the problem. In the future, remember never to skip your regular HVAC maintenance. You have no idea how much money you can save by taking good care of your appliances.



ECM Air Conditioning, with its headquarters located in Boynton Beach, FL, provides air conditioning services within Palm Beach County, Broward County, Martin County, and St. Lucie County. If you’re looking to have a new HVAC system installed, we’re on-call and ready to assist you. So if you’re in need of an HVAC installation, don’t hesitate to contact us today to schedule an inspection! Our HVAC installation experts will check your ductwork, measure, check wire sizes, and more before making recommendations to ensure maximum efficiency and comfort. Call us at 561-295-1763 or contact our HVAC installation team online by clicking here.


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