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Air Conditioner Making Loud Buzzing Noise

Air Conditioner Making Loud Buzzing Noise: What To Do?

In Phoenix, air conditioners are an essential home appliance. So it’s natural to be concerned when your air conditioner is making a loud buzzing noise. In this post, we’ll provide you some guidance on how to deal with a buzzing AC unit, including when to call a professional.

Common Reasons Your Air Conditioner is Making a Loud Buzzing Noise

#1. AC Humming Can Be Caused by Loose Components

One common cause of AC humming is loosely-secured internal components. Bearings, for example, can vibrate when not secured properly within the unit, producing a continuous hum. The same goes for a failing motor or starting capacitor.

What To Do

Unless you’re a trained professional, it can be difficult to accurately and safely identify which AC components are responsible for the humming. If you’re in the Phoenix area, contact American Home Water and Air and we’ll have a technician solve the issue promptly. Outside of Phoenix and the surrounding areas, call up your local trusted HVAC service provider.

#2. An Air Conditioner Humming Inside Can Be the Result of Debris

If your outdoor AC is making a humming noise inside, it’s possible debris has gathered in the condenser coils. The wind has a way of blowing leaves and twigs into the coil openings and even further inside the machine.

What To Do

If you suspect the debris has made its way inside the unit, you’ll need to have a professional open it up safely. First, however, brush away any debris yourself with a small-handle broom and give the coils a good cleaning with water and coil foam cleaner.

If this solves the issue, you’re good to go! Clean the coils periodically to avoid it happening again.

#3. Refrigerant Leak: Another Common Cause of Air Conditioner Buzzing

Refrigerant leaks can cause your AC’s internal components to freeze and vibrate more than they should. This can also occur if your unit has been running for too long, as is prone to happen during Phoenix’s long and hot summer months.

Read this article on how to save on air conditioning bills during the summer months in Phoenix.

What To Do

If your air conditioner is humming inside and you’ve had it on for a long period of time, first turn it off for a few hours. This should be enough time for the internal components to thaw if they are indeed frozen.

If the AC keeps making a humming noise from inside, you’ll need to have a professional investigate for a potential leak.

#4. AC Unit Humming But Not Turning On? It’s Possible An Electrical Issue

If your AC unit is humming but not turning on, it’s a fairly reliable sign of an electrical issue. The contractor relay switch (which lies in the outdoor unit and connects to your home thermostat) is a common culprit for buzzing noises.

It’s also possible that electrical connections are to blame for your AC unit humming but not turning on. 

What To Do

Regardless of what the issue turns out to be, if you suspect it’s electrical you should definitely contact a professional. Attempting to service your AC’s electrical components on your own can put your safety and the unit’s proper function at risk.

If you’re wary of calling a professional for financial reasons, consider some of the other methods we recommended above (like cleaning the coils) to see if that solves the problem.

#5. Improperly-Configured or Broken Compressor

Another common reason your air conditioner is buzzing but not running could be a broken or improperly configured compressor.

The compressor is what ensures your unit’s refrigerant is at the right pressure and temperature. If the compressor is receiving an improper voltage, buzzing can occur. The compressor can also break over time and is one of the more commonly replaced AC components.

What To Do

Contact a professional and have them look at your compressor if your air conditioner is buzzing but not running and the DIY solutions we mentioned above haven’t helped.

#6. Missing AC Unit Isolation Feet

At the base of most AC units, you’ll find rubber feet. These can crack (particularly in the Arizona heat) over time and cause your AC unit to vibrate improperly, which produces a buzzing sound.

What To Do

These rubber feet (technically called “isolation pads” or “anti-vibration pads”) can generally be replaced without the help of a professional. Make sure you cut off the unit’s electricity while you do the installation for optimal safety. The process is much easier with an extra pair of hands since you’ll need to tilt the AC unit to install these anti-vibration pads.

Other Common AC Noises

Buzzing isn’t the only sound a malfunctioning AC makes. Here’s a quick rundown of other common sounds that signify an issue.


If your AC is making a loud mechanical screaming noise, worn-out bearings may be to blame. Another common culprit is a slipped belt between the unit’s blower and motor. Either issue requires professional attention.


If the sound you hear is a less consistent rattling, something has almost certainly come loose within your AC. It could be a bearing or even a stone that got sucked into the unit somehow. Either way, contact a professional and have them open the unit up to remove the item.

Repeated Clicking

Your air conditioner naturally clicks when it shuts on and off. If you hear it clicking randomly, a relay switch could be faulty. A technician can replace or repair this switch with ease. You can read our article on “AC unit blows hot air” if you feel like your AC is not cooling the way it did before the noise issues.

Air Conditioner Making A Loud Buzzing Noise: Conclusion

If your air conditioner is making a loud buzzing noise, there are many possible explanations. In this post, we listed a few of the most common ones. Because of the wide range of possibilities, you need a technician you can trust — one that won’t try to sell you “fixes” that you don’t actually need. That’s why it’s important to know a thing or two about the main parts of your AC system.

At American Home Water and Air, we’ve been providing Phoenix residents AC installation and maintenance services for more than 30 years. Our technicians act with integrity — and we don’t pay them a commission based on what parts of upgrades they sell to customers. Our technicians are compensated fairly for their work, ensuring transparent pricing and efficient service for you.

Whether your AC is buzzing or you’re experiencing some other issue, we’d be honored to lend you a hand.

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