Why Is My AC Making a Loud Buzzing Noise?

June 14, 2022

When you hear unusual sounds from your central air conditioning unit, it’s always worth paying attention. While some amount of noise is inevitable, there’s always a reason for a change in noise level — even if it doesn’t ultimately indicate a problem.

Today, we’ll discuss the reasons your AC unit might be making a loud buzzing or humming noise, and whether it might mean there’s a problem.

Be cautious if you have any reason to suspect the noise you’re hearing is electrical in nature, as electrical shock or damage to your home can result. If that’s the case, or you have any doubts, you should immediately contact an expert for air conditioner repair.

7 Reasons Your Air Conditioner Is Making a Buzzing Sound

While these aren’t the only possible causes, these are the most common problems with your air conditioner that would cause a buzzing sound;

  1. The contactor relay switch: This low-voltage switch in your exterior unit is controlled by the thermostat in your home. It can cause a buzzing noise when malfunctioning, but fortunately, it’s an easy component for a technician to replace.
  2. Circuit breakers: Problems with the circuit breakers of your home or system can lead to a buzzing sound in your AC. This becomes far more likely if you find yourself frequently flipping breakers back. The solution might involve an electrician replacing your panel rather than HVAC work.
  3. Fan problems: There are several fans throughout any AC system, both on the exterior and interior systems, as part of the process of moving heat. A malfunction that causes any of these fans to work improperly can result in a buzzing or humming noise.
  4. Electrical connections: Problems with electrical connections throughout your system can lead to arcing, which can make a humming noise. Regular AC maintenance helps keep these connections tight and will detect degradation early. Even if they don’t reach the point of arcing and dangerous shorts, you’ll be wasting electricity on poor connections.
  5. Frozen unit: Frozen evaporator coils, in combination with the moving parts of fans and motors, can lead to a humming or buzzing sound. You can resolve this in the short term by turning your AC off and letting it thaw completely and dry out. You’ll want to clean it and replace your filter to prevent a recurrence — if it keeps happening, you’ll need an expert to help.
  6. Resonance and vibrations: Your AC has moving parts like the fan, especially the large one on your exterior unit, which can cause vibrations and resonance with ductwork or the surface the system rests on under some circumstances. This becomes far more likely if something shifts out of place or a fan starts malfunctioning.
  7. Duct obstruction: If airflow gets obstructed at your AC filter or elsewhere in your ducts or registers, it can cause vibrations or buzzing noises from air passing through smaller areas with more force. Change your filter, open registers, and check for blockages.

What To Do if You Hear a Buzzing Sound Coming from Your AC Unit

When you hear any buzzing noise, you’ll want to act immediately to resolve the problem — or at least identify the root cause, if it’s something innocuous like vibrations. Running an AC that’s malfunctioning, even if it still works correctly, can damage it substantially or expose you to safety hazards.

If your AC is making a buzzing or humming sound and you need professional AC repair in the Cincinnati area, contact Rick’s Heating & Cooling at (513) 899-6005.

We’ve been repairing air conditioners throughout the Morrow and Cincinnati metro areas for over 30 years!