Man fixing an air conditioning unit with a screwdriver, with the words, why is my A/C noisy.

The intense heat from the hot summer months has many people keeping a closer eye out for their air conditioning unit. A broken unit in the middle of a hot summer day can leave your house feeling like an oven, so it seems natural that you would do everything in your power to prevent that from happening. When your air conditioning unit begins to grumble, it can be a potential sign that there is a problem beginning to arise, such as a loose bolt or broken fan. This article focuses on why your air conditioning is being noisy and if those noises are a cause for concern.

Age of the Air Conditioning System

Naturally, your air conditioning unit makes some sort of noise, such as a low hum, when it is running. If you live in an older home, your air conditioning unit may be louder than a newer model. Newer models have the newest innovation in sound barriers, allowing them to run quieter. If the noise of your older unit is bothering you, you can have an HVAC technician install sound blankets to dampen the noise. Hearing consistent but loud sounds are normal for an older air conditioning system. If you notice the sound increasing or your unit is new, then the sound is a warning of a bigger problem.

Rattling Sounds

If you hear a rattling sound covering up the gentle hum of your air conditioning unit, then this is a sign that there is an issue. Leaves, sticks, and other debris may have become lodged into the air conditioning vents. This is a common issue for those who have a split system with an outdoor unit. You will want to clear away any leaves or debris that may be caught in the vent grates and call an HVAC technician to clean the inside of the vents. This will help reopen up the airflow and allow your system to run more efficiently and quietly.

Another cause of the rattling sound could be loose bolts, screws, or a fastener within your unit. If you can find these bolts or screws, you can easily tighten them yourself. If you cannot locate them or feel that they are out of reach, you will want to call a professional HVAC technician for help.

If none of the issues above are the cause of the rattling, then there is a high possibility that the compressor motor is failing. As the compressor ages, the motor begins to die resulting in a strain to keep the compressor operating properly. This causes the motor to start to sputter creating vibrations that we hear as a rattling sound. If this is the case, you will want to get the compressor motor replaced as soon as possible, as a broken compressor will eventually cause the whole unit to shut down.


Proper maintenance for your air conditioning is making sure that any moving parts are lubricated yearly. This helps avoid them from scraping together and increasing the wear on them. If your unit is making a grinding sound, it is a sign that moving parts are scraping against each other. You will want to turn off your unit and lubricate these parts before continuing use. This will allow you to save your parts from extensive wear and increase their lifespan. If this doesn’t fix the problem, you are probably facing a worn fan motor bearing and it needs to be replaced.

Popping or Hissing

Any kind of popping or hissing sound is an indication that something isn’t working in your ductwork. This could be as simple as a dent has occurred from debris or there is a faulty seam, allowing some of the air to escape. The only other possibility is that there is a refrigerant leak but this will be more noticeable as the sound is accompanied by moisture or leaking liquid. You will want to hire an HVAC technician to come and fix the seam or refrigerant leak.

If you are still unsure what is causing the noises of your air conditioning unit or you need to have it inspected and repaired, call the technicians at Cote’s Mechanical. They are dedicated to excellent customer service and providing high-quality repairs. Their years of experience can help them pinpoint the problem quickly and lead to a resolution that will have your AC running as if it was brand new. Contact Cote’s Mechanical Heating & Air Conditioning today for a consultation.