Noisy AC Unit?


Your air conditioner should run quietly, with just a little sound from the circulating and condensing fans. As your unit ages, you may notice it making more noises, and sometimes they are very loud. Here are the sounds you may hear and what you can do to solve them.


Every air conditioner will develop some rattles as it ages, especially without routine maintenance. Rattles typically mean something’s loose or there is something caught in your system.

Many rattles come from the outside of the condensing unit and may be as simple as a loose fan blade or fan cage. It could also be a loose piece in your compressor bouncing around. Something like a twig may have also gotten in your condensing unit, causing it to rattle as the unit runs.

Buzzes and Hums

Buzzes and hums typically mean there is an electrical issue of some form, which is what generates the sound. In either the inside or outside unit, a failing fan motor can cause this sound. You may notice the fan is either spinning really slowly or it will not spin at all.

The other common culprit for buzzing is the capacitor in the condensing unit. This component holds a large electric charge to start the compressor. You will likely be able to hear the buzzing inside your home and will notice the compressor fails to start.


Another component outside is the contactor, which acts as the switch to start the compressor. The thermostat sends a signal to the contractor, which then allows the current to pass through it. This then allows the capacitor to send its charge to the compressor to start.

When this component goes bad, it will either get stuck open or it will rapidly open and close. This rapid movement causes the chattering sound as the contact points hit. The major concern over a bad contactor is the damage it causes compressors by making them rapidly cycle.


You have probably heard the squeal a car makes when it has a loose fan belt. Your air conditioner may make the same kind of sound, and yes, it is likely the fan also.

However, the cause may not be the same. While some systems still use belts that may make this sound, a failing fan motor will as well. Worn bearings are the more common cause of this squealing in most modern systems.

Screaming or Hissing

Your system should never sound like someone screaming in a horror movie. However, that doesn’t stop it from happening from time to time. Screaming, hissing, and even bubbling may indicate you have a refrigerant leak.

If you hear this sound, shut down your system immediately and call for a repair technician. Not only will this damage your system, but a leak inside poses a health hazard.

How to Solve These Noises

All of these noises are because of loose or worn areas of your system. The best way to solve and prevent them is to have regular maintenance for your system.

A technician will check all the connections around your system to ensure they are tight, which solves most rattles. This includes your fan mounting bolts, and the screws holding your condensing fan blades in place. Your technician also lubricates the bearings of the fans, which prevents and solves squealing sounds.

Your technician also tests the electrical components to ensure they are operating optimally. This is especially important for the capacitor and contactor in the condensing unit. If either tests bad, you can replace them before the noise gets bad and the problem damages your system.

They test your refrigerant level as well. While this may not solve a noise on its own, if it’s low it does indicate a leak. The leaks not only can cause substantial sounds, but they also damage your coils and compressor by causing system freezes.

While they are there, your technician will clean the circulating fan and both coils. This helps ensure air can flow freely through your system, maintaining its efficiency. This helps prevent extra strain on the system that will lead to some problematic noises.

For over 25 years, Guaranteed Comfort Heating & Cooling has offered expert air conditioning repair to those around Windsor, ON. Our expert technicians offer heating, air conditioning, and water heater installation, repair, and maintenance. Call to schedule your air conditioning maintenance today.

Chris Egan


Chris Egan, owner of Guaranteed Comfort Heating & Cooling, brings over 35 years of HVAC experience. Dedicated to customer satisfaction, he delivers top-notch heating and cooling solutions.