air conditioner making noiseA soft hum coming from your AC unit is nothing to worry about. In fact, you probably don’t even notice these sounds in your day-to-day activities. But when you start to hear strange sounds, you will definitely notice.

If your air conditioner is making noise, read on. We’ll cover all the possible AC sounds and tell you exactly what they mean.

Buzzing Sound

If your AC makes a noise that sounds like buzzing, there could be several issues with your unit.

A buzzing sound could be a problem with the compressor. This is that part of your AC that pressurizes and cools the refrigerant. Buzzing sounds may mean that the compressor is malfunctioning.

Another possibility is that refrigerant is leaking. When this happens the AC can freeze, even in the middle of a hot summer.

If your unit has any loose or missing pieces, that can cause wear and tear on other parts of the unit. This can cause the buzzing sound you are hearing.

Finally, a buzzing sound coming from your AC can be due to missing or broken isolation feet. Your compressor sits on small rubber feet. The rubber on these feet can crack or wear out over time. When unbalanced, the compressor may make a buzzing sound.

Whining or Whistling Noise

Whistling and whining noises tend to signal airflow problems.

One reason for these sounds may be due to incompatible ducts or HVAC equipment. If you have an older unit that has had various parts replaced, it’s possible that the pieces don’t fit well together.

The ductwork might be too narrow for the air blowing through the unit causing these annoying sounds. Or the ducts could be cracked which causes a whistling sound.

When your AC makes a noise like a whining sound, it could be a case of clogged filters. When your air filters become full of dust and debris, they become blocked.

Luckily, this is a simple fix. Just replace or clean your air filter.

Screaming Noise

If you hear a high-pitched screaming sound, act quickly. Turn off the AC and call a professional immediately.

That screaming sound might be a sign of high internal pressure in your compressor. This is very dangerous.

Banging Sound

A loud banging is most often a sign that your AC unit has a loose or broken part inside the air compressor. It could also mean that it’s time for a new compressor. Or it could mean that the indoor blower might be unbalanced.

Call your local HVAC specialist to come to find the problem and suggest a solution.

Rattling Noise

Rattling usually is due to loose parts. In your AC system, there are several parts that move constantly such as motors. Over time, these parts can come loose. So can ducts.

The rattling sound you hear might be loose screws. Or the unit might not be correctly fastened to the concrete footing.

Humming Sound

When you hear a humming sound coming from your AC, that is typically an issue with the fan.

Your AC fan needs regular maintenance to keep it clean and in good working order. This humming sound could also mean that the fan motor has a problem or that one of the blades has become bent.

Squeaking or Screeching Noise

A high-pitched sound coming from your AC can be extremely aggravating. If this happens to you, contact an HVAC professional.

Chances are that there is an issue with your unit’s fan motors or the compressor. Squeaking or screeching sounds usually indicate unlubricated bearings or damaged blower belts.

Hissing Sound

A hissing sound coming from your AC may be a sign of a dangerous refrigerant leak.

Usually, this is accompanied by a system that runs more often than usual. You may also notice that your home is not as cool.

If so, you will need to have your refrigerant charge, coils and lines checked for leaks.

Keep in mind that refrigerant leaks are often due to neglected maintenance. When coils aren’t cleaned regularly, they can become corroded and leak.

A regular preventative maintenance schedule will help you avoid these issues in the future.


A clicking sound when the AC unit turns on and off is normal. But, if you hear a constant clicking, that is a problem.

This could be a sign of a failing thermostat or a defective control. Anytime there is an electrical issue, act quickly before they develop into bigger issues.

Constant Running Sounds

When your AC is running, it makes a muted humming sound. You should hear the AC turn on and off throughout the day as it regulates the temperature.

Yet, if your AC is constantly running, that is an issue. Problematic AC coils might be the source of this noise. Bent or clogged coil fins can cause your AC to become inefficient.

That means that the system has to run constantly and work harder to cool your home. If you don’t fix it, the constant taxing of the system will lead to a complete breakdown of your AC unit.

Call the Experts When Your Air Conditioner Is Making Noise

Thanks for reading! We hope that this guide on the various AC noises has helped you pinpoint the noise your unit is making.

The best thing you can do is to call Guy’s AC & Heating. For over 35 years, we have been providing quality residential and commercial HVAC services to the local Houston, TX and surrounding area.

Contact us today so we can come to give you a free estimate. We are happy to give you a second opinion as well.