Why Is My AC Making a Loud Noise? A Florida Tech Answers

May 28, 2020

If your AC system is making a loud noise, chances are there’s an issue with your AC that you don’t want to ignore.

Your AC system can make a variety of loud noises, but a few of the most common include:

  • Hissing
  • Banging
  • Clicking
  • Buzzing
  • Squealing

Below, we’ll look at each of these noises and give you an idea of what may be causing them so you know how to move forward.

Have a noisy AC and need a professional's help? No worries, we’ve been working with all kinds of AC issues for years, so no matter what’s going on with your AC, we will be able to diagnose and fix it for you as soon as possible. Learn more about the AC repair services we offer

Loud Noise #1: Hissing

If you hear a hissing noise coming from your AC system, the most likely reason is that there’s a leak in your refrigerant line.

Refrigerant is a substance that runs through your entire AC system, from your indoor unit to your outdoor unit and back. Refrigerant absorbs heat from your home’s air and carries that heat to your outdoor unit where it dumps that heat outside. Then it circles back to your indoor unit to carry more heat outside.

Heat Pump Diagram

But, if there is a leak in your refrigerant line, the escaping refrigerant can make a hissing noise as it leaks out.

If you do have a refrigerant leak you’ll also probably notice:

  • Warmer air coming from your supply vents
  • Ice on your refrigerant lines
  • Higher energy bills

If these symptoms sound like what’s going on at your house, you should reach out to a professional. A professional will need to repair the leak and then recharge your refrigerant.

Loud Noise #2: Banging

A banging noise can be caused by a variety of issues, so we’ll split this up into:

  • Banging noise coming from inside your home
  • Banging noise coming from outside your home

If the banging noise coming from inside your home...

If you hear a banging noise coming from inside your home, it’s probably:

  • A loose fan mount- Over time, the mounts that hold your blower wheel stable can become loose or unstable. If this happens, it can cause your fan to hit the casing of the AC unit, which can make a banging noise. If you think this is your issue, you’ll need to reach out to a professional to repair or replace this part.
  • An air filter issue- Your air filter is placed in front of your return ducts, which are the ducts that suck air into your AC system. Sometimes, these return ducts are placed on the ceiling, and when they suck in air, they can suck the air filter up as well. As soon as they stop pulling air in, the air filter falls back down, which can make a banging noise. If your air filter is getting sucked up against the top of the duct box, you likely have a dirty air filter or your air filter is too restrictive. If you recently purchased a high-efficiency air filter (MERV 10+), it could be restricting the airflow into the system, which can cause the filter to get sucked up. If you just have a basic air filter, it may just be dirty, so our suggestion would be to replace your air filter and see if this stops the banging noise.
Dirty Vs Clean Fiberglass Air Filter2

If the banging noise is coming from outside your home...

You’re probably dealing with:

  • A loose fan- The fan in your outdoor unit can also become loose and hit the casing around it, making a banging noise.
  • A loose refrigerant pump- Your refrigerant pump is held in place by springs. But if those springs are damaged or aging, it can cause your refrigerant pump to hit the side of your compressor, which makes a banging noise.

If you think you have a loose fan or a loose refrigerant pump, you’ll need to reach out to a professional for help.

Loud Noise #3: Clicking

A clicking noise is usually an indication that your AC is trying to turn on, but for some reason, cannot.

This is usually the result of:

  • Thermostat malfunction
  • Wiring issue
  • Faulty relay
  • Dead capacitor (“battery” that helps power your outdoor AC unit)
  • Broken contactor (the “switch” that turns your outdoor AC unit on)

Regardless of the issue, if you hear a clicking noise, you’ll need to reach out to a professional for help, and we’d suggest sooner rather than later. As we mentioned above, a clicking noise usually means your AC system is trying to turn on but can’t, which means you’ll likely be stuck without cool air until the issue is fixed.

Loud Noise #4: Buzzing

If you hear a buzzing noise, that usually means there’s an electrical issue with your system.

If the buzzing noise is due to an electrical issue, it’s likely coming from:

  • An electrical connection
  • AC circuit breakers (buzzing would be coming from the electrical panel)
  • Contactor (As we mentioned earlier, the contactor is a relay switch that lives in your outdoor AC unit. It turns from low voltage to high voltage when your thermostat signals it to)
  • Condenser fan motor (this is in the outdoor unit, so you would hear a buzzing from outside)

However, there are a few other reasons your AC could be making a buzzing noise, including:

  • Damaged compressor isolation feet- Your compressor, which sits in your outdoor AC unit, is held up by isolation feet. Over time, these start to break down, which can cause the compressor to move slightly when your AC is on, making a buzzing noise
  • Frozen AC- If there is a leak in the refrigerant line, it can cause parts of your AC to freeze up, which can make a buzzing noise.
  • Loose parts-There are a variety of parts that can become loose and make a buzzing noise when your AC is on. If your AC is older (10 years) or you recently had your AC maintained, this could be the cause of the noise.

No matter which of the above issues you have, you’ll need to reach out to a professional for help. All of these repairs/replacements can be difficult to do and you’ll want a trained expert to handle it for you.

Loud Noise #5: Squealing

If you hear squealing coming from your indoor unit, it’s likely the fan belt that is frayed or misaligned.

The fan belt connects the motor and the fan, but over time, it can wear out which can make a screeching or squealing noise. The belt could have also just become misaligned, in which case it will make a squealing noise as well.

If you’re hearing a pretty regular squealing noise coming from your indoor AC unit, this is likely your issue, and you’ll want to contact a professional to come and realign or replace your fan belt.

Want your AC to stop making loud noises? Call Red Cap

More than likely, if you have one of the issues listed above, you’re going to need a professional to come and diagnose and fix the issue. We have quite a few years of experience under our belt, so no matter what is going on with your AC system, we should be able to diagnose the issue and repair it quickly.