Air conditioning is what makes home life comfortable during the warmer months. If your AC runs loud though, your comfort can turn into irritation quickly. So what should you do when you start hearing buzzing, screeching, or vibrations coming from your AC system?

Why Your AC Runs Loud

It can be scary to hear your AC making loud noises all of a sudden, but it’s usually nothing to be alarmed over. Just check to see if one of these issues is the source of the noise:

Faulty Contactor Relay Switch

A common complaint is to hear a nearly constant buzzing sound coming from the condenser unit outside. The noise can appear when the unit is running or not due to the fact that it’s most likely being caused by a defective contactor relay switch.

This low-voltage switch is what signals the condenser to turn on when the thermostat settings are changed. When it fails though, the switch can cause a steady buzzing sound.

How to Diagnose

The bad news is that contactor switches are fairly complex and difficult to test with a multimeter, although it is possible. The good news is that they’re cheap and easy to replace, so if this description seems to fit your situation, try replacing the switch.

ac making loud noises

Image from North America HVAC

Defective Fan Motor

If you hear a screeching or buzzing only while the unit is running, you may have a problem with your condenser fan motor which is why your AC runs loud.

This motor is what turns the large fan blades that draw air over the condenser during operation. Broken motor bearings can cause a loud screech, while a motor that won’t turn at all may simply buzz loudly.

How to Diagnose

Stand next to your AC unit outside and have someone else turn the thermostat on and off. If the noise you hear is coming from the fan motor and only appears when the unit is running, the part may need to be replaced.

air conditioner loud

Image from Silicon Beach USC

Compressor Runs Loud

The compressor is the beating heart of your air conditioning system, but for some reason, certain models seem to run much louder than others.

Proximity to windows can also be an issue, so once you know the noise is coming from the compressor, you’ll need to deaden the sound somehow.

How to Fix

Shut off the power and access the inside of the unit. Remove any leaves, sticks, or other debris you find, and tighten all screws and connections. You can also purchase a compressor sound blanket online which helps significantly and is easy to install.


noisy ac compressor

Image from Blandare


Call Tiger Mechanical right away if your AC runs loud after inspecting these parts, and one of our experienced technicians will help bring some silence back to your life.