If you’ve ever heard an air conditioner hiss, you know it’s not a good sign. In this article, we discuss what that sound means as well as other common sounds like banging and clicking.

Abnormal Sounds

When the sun is absolutely baking, your natural instinct is to crank up the air conditioner.

What isn’t natural is for your home cooling system to make the following sounds:

  • Hisses.
  • Bangs.
  • Clicks.

Should you discover that your AC is making some unsettling noises, there are a few things you can do:

1. Air conditioner hiss

Your AC should run smoothly and quietly. It shouldn’t sound like a balloon or tire slowly deflating.

If it does emit a persistent hiss while in operation, it usually means maintenance is required on one – or both – of the following:



NOTE: If it’s the thermostat, get it checked out ASAP.

Hissing coming from the thermostat indicates there’s an electrical issue taking place, such as:

  • Short circuit.
  • Disconnected/loose wiring.
  • Excessive amperage.

Live wires are dangerous. If left unattended, it could cause significant damage to your thermostat. In the worst-case scenario, an electrical fire might start.


NOTE: If there’s a system leak, get it looked at ASAP.

The lines transporting AC refrigerant can become ripped or torn. When that happens, refrigerant escapes and your air conditioner can’t actually provide cool air.

Here’s why this needs to be addressed immediately:

  • Should too much refrigerant get wasted, the compressor might fail outright. Without a compressor, your AC is essentially useless.
  • Even with the smallest line leak, you’re paying for an AC that cannot properly cool your home.

System leak repair is a three-step process:

  • First, the leak itself has to be detected.
  • Then, the leak has to be sealed.
  • When that’s done, any lost refrigerant must be replaced.



  • Loss of Freon (a common refrigerant) is damaging to the environment. If not handled by a licensed, qualified technician, that small leak can become a big environmental hazard.
  • In some instances, systems leaks are too severe and cannot be repaired. If that’s the case, the sensible option is to replace the unit.

2. Air conditioner bangs

Any banging sounds – no matter how tiny or insignificant they seem – shouldn’t be ignored.

Instead, have a Woodbridge GTA ClimateCare technician take a look inside your unit. Chances are they’ll discover the banging is due to the following:


When your air conditioner bangs (especially if it’s constant), it usually means there’s a loose or dislodged part inside the housing.

Usually, it’s one of the following components:

  • Blower unit.
  • Connection rod.
  • Piston pin.
  • Crankshaft.



Remember, your AC cannot function without a compressor.

So, if there’s a perpetual banging sound, it could signify the compressor needs to be replaced. Especially if the following takes place along with the bangs:

  • Your AC feels like it’s overheating.
  • The motor won’t start at all.
  • Your air conditioner repeatedly turns on and off.

3. Air conditioner clicks

Clicks are usually the easiest sounds to spot and diagnose.

Now, if your AC clicks when it’s running, try to note when and how often the clicks occur. That’ll provide a clue as to exactly what’s going on.


NOTE: Do not try to fix this yourself.

If your AC makes a single click at start-up, that’s fine. It means your thermostat is telling the capacitors to get to work. It gets problematic if the clicking noise is constant, but the air conditioner cannot turn on.

That means the thermostat is doing its job, but the capacitors are unresponsive due to:

  • Shorted wires.
  • Faulty control board relay switch.


Does the clicking sound feel like it’s coming from outside? If so, there could be something going on with the compressor.

Sometimes, it could be as simple as a loose bolt or refrigerant tubing. The best way to know for certain is to have us look at it for you.


When your AC clicks, does it start slow and get louder and faster?

Yes? That means something is inside the housing and hitting the fan blade.

It could be a branch, stone, or even a loose part of the fan itself.

Hear any of these three sounds? Hear something else? Call us ASAP.

You don’t want your air conditioner to fail on the hottest day of the year. And you don’t want to spend money on annoying AC repair, either.

Your best bet is to contact us immediately if your air conditioner makes the noises listed in this blog – or any other sounds that you’re concerned about.

Contact us

Sign up to receive helpful home comfort tips and reminders

  • This field is for validation purposes and should be left unchanged.
climatecare logo
energystar logo
hrai logo
tssa logo
wsib logo