Patrick Riley
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Why is My Air Conditioner Making a Loud Buzzing Noise? A Phoenix Tech Answers

October 02, 2019

If your AC is making a loud buzzing noise, you’re likely dealing with:

  • An electrical issue
  • Loose parts
  • Frozen evaporator coil
  • Damaged isolation feet

Below, we’ll walk through each of these issues in more detail, so you can determine why your AC is buzzing and whether or not you need to call a technician to fix it.

Rather speak with a technician right away? That’s what we are here for. Learn more about the AC repair services we offer or…

Buzzing Noise #1: Electrical issue

If your AC is making a loud buzzing noise, the most likely answer is that there is an electrical issue.

Sometimes, an electrical current escapes the intended path and jumps between circuitry, a phenomenon called electrical arcing. If you are experiencing arcing, your AC will likely make a buzzing noise.

The buzzing noise could also be from one of the following components:

  • Loose wiring
  • Failing or damaged condenser fan motor
  • Malfunctioning compressor
  • Contactor relay switch (switch in the outdoor unit)
  • Bad capacitor

The above issues are usually the result of normal wear and tear over time.

The solution: If you think you may have an electrical issue, you should turn off your AC system and reach out to an experienced tech. If you do have an electrical issue, continuing to run your AC could cause long-term damage and expensive repairs.

Buzzing Noise #2: Loose parts

Over time, parts of your AC unit can become loose and may start to rattle around when your AC system is turned on. Depending on the part that’s loose, it can sound like your AC is buzzing or shaking.

The solution: You’ll need the help of a tech. They should be able to quickly diagnose what part(s) are loose and repair them.

Buzzing Noise #3: Frozen evaporator coils

Evaporator coils are the part of your AC system where heat is transferred from your home’s air to refrigerant, which takes that heat outside and dumps it.

Refrigerant is very cold, but your evaporator coils keep from freezing because of a consistent flow of warm air from your home that gets blown over the evaporator coils.

Warm air from your home is blown over cold evaporator coils, where heat is absorbed by refrigerant. The result is cool air that is then pumped back into your home.

However, if there isn’t enough warm air blowing over these cold evaporator coils (or refrigerant levels are low), these coils can freeze over, which can cause a sort of buzzing noise.

The solution: First, turn your AC system off. If your evaporator coils are frozen, it could damage your AC to keep running it.

Step 1: Check your air filters. If your air filters are dirty and clogged, they could be blocking airflow to your evaporator coils, which can cause them to freeze over.

Dirty air filter

If your air filter looks like the one on the right, it's time to replace it

Step 2: If you’ve checked your air filter and it’s clean, the next step is to check your return and supply vents. Are they open and unobstructed by items like furniture? If not, open them and remove any obstructions in front of them.

Step 3: If you’ve checked your air filter and vents, it’s time to call a technician. You likely have a refrigerant leak or a malfunctioning blower. Unfortunately, if either of these is your issue, you will need to have a professional come to assess and repair the problem.

Buzzing Noise #4: Damaged isolation feet

Your AC compressor is the “heart” of your AC system. It sits in the outdoor unit of your AC system and its job is to pump refrigerant in and out of your home (transferring heat out).

Inside the outside unit, your compressor is held up by “isolation feet,” which are rubber feet that hold the compressor in place.

home ac compressor replacement in phoenix

A compressor held up by isolation feet inside the outdoor AC unit.

As your AC system begins to age, these “feet” can become damaged or start to break down, which can cause your compressor to become unstable. If your compressor is loose in your outdoor unit, it can vibrate or buzz when your AC is turned on.

The solution: Contact an AC technician. They should be able to tell if your compressor has worn out isolation feet and replace them if necessary.

Not sure it’s a buzzing noise you’re hearing?

Sometimes it can be hard to tell exactly what kind of noise you’re hearing from your AC system.

Here’s a list of other common AC noises that you may hear from your AC system:

  • Banging, typically the result of a (very) loose or broken compressor
  • Hissing, most likely a refrigerant leak
  • Squealing, a bad compressor or damaged fan motor
  • Clicking, an electrical issue or debris in the blower motor

If you think the noise you’re hearing is more closely related to one of the above, you should contact a professional. They should be able to diagnose the noise and make any necessary repairs.

Still having issues with your AC? Hire Phoenix’s time of pros

If you’re still having issues with your AC system, our suggestion is to contact a technician. Although it may not seem like a big deal, a buzzing AC could lead to some expensive repairs (or even a replacement) if it’s not taken care of in a timely manner.