Why Is My AC Unit Buzzing Every Few Minutes?

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Updated August 12, 2022

Even the best air conditioner can develop issues over time, and it can be worrisome to hear loud buzzing sounds coming from your unit. Luckily, simple measures like changing the air filter, inspecting the coils, and ensuring the AC unit is stable can stop this strange sound. Stick around to learn, “Why does my AC unit make a buzzing noise?”

KEY TAKEAWAYS:

  • Momentary buzzing from your AC unit is a common noise, especially on high-temperature days, and is nothing to worry about.
  • Loud humming sounds may indicate that a fan blade or electrical component has come loose inside the housing.
  • A prolonged buzzing noise might also signify a frozen evaporator coil or a faulty compressor.

Insider Tip

A dirty air filter can suffocate your air conditioning system, leading to strange noises and extra power consumption.

Why Is My Air Conditioner Buzzing?

Whether your AC hisses or makes an electric murmuring sound, these noises can indicate serious problems with the AC hardware. For example, if you hear a pulsating noise when your AC starts, you likely have loose components or debris in the system. That said, some everyday noises do not indicate an issue, and you can take specific steps to reduce the AC’s noise level.

Condenser Fan Motor Issue

When your air conditioning unit runs, the condenser fan motor blows air pulled in by the outdoor unit. Over time, dirt and debris become lodged inside, preventing the fan blade from spinning. If the outdoor fan motor cannot function, it produces a buzzing or rattling noise. The humming sound can occur if the condenser coils and fans are dirty.

Loose Parts

Internal electrical components that aren’t adequately secured commonly cause buzzing inside your AC. When bearings are not correctly connected within the unit, they can vibrate, resulting in a continual hum. These little parts and loose electrical connections impact the efficiency of your air conditioner and contribute to more costly difficulties over time.

Compressor Issue

The compressor in your air conditioner pressurizes and chills the refrigerant. A faulty compressor motor can create a buzzing sound if there’s a misalignment or electrical issue. Replacing the compressor is a standard repair service since it is normal for a compressor to fail over time.

Frozen AC Unit

Refrigerant leaks can cause your AC’s internal components to freeze and vibrate. If you have a frozen air conditioning system, turn it off and let it thaw for a few hours. If the humming noise returns, schedule a technician for air conditioning repair services.

Warning

If the loud humming sound doesn’t stop or the volume increases, you may damage the entire unit by not shutting it off. Contact an HVAC professional immediately.

Broken Isolation Foot

The compressor for the air conditioner is nearly always located at the bottom of the unit. It is typically supported by a little rubber foot, often known as an isolation foot. Over time, the rubber on this piece can break or deteriorate. This causes the compressor to become imbalanced, creating a buzzing noise when the air conditioner runs.

STAT: According to a 2020 US EIA (Energy Information Agency) survey, 2% of Americans do not have control of their air conditioning equipment. (source)

Why Does My AC Unit Make a Buzzing Noise FAQs

How do I reduce internal AC noise?

As long as your AC unit is operating normally, you can use a sound blanket on the outdoor unit to reduce the noise of the AC system. In addition, you can insulate your air handler closet if your system is indoors.

What is a capacitor?

The capacitor is a small electrical component that helps start the compress, outdoor fan motor, and the blower motor in the indoor unit. A lousy capacitor will prevent your AC system from starting and running.

Is it better to repair or replace the AC unit?

EnergyStar recommends replacing your AC unit every 10 to 15 years. So, if your AC unit breaks and is nearing a decade old, it is an excellent time to replace the system.
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