What AC Noises Could Mean Big Trouble for Your Unit?

You’ve probably gotten used to the soft humming noise your indoor and outdoor air-conditioning equipment makes when running normally. Other strange sounds may get you worrying about having to spend hundreds or thousands of dollars on repairs. However, while some sounds are a definite sign of a problem within your system, others, like clicking, can be either harmless or a cause for concern depending on when you hear them. Here’s a closer look at the AC noises that could signal trouble.


When your air conditioner first turns on or shuts down, you may hear a fast clicking sound from the thermostat. That clicking noise is normal. However, if you hear it repeatedly during the cooling cycle, you may have electrical problems with the capacitors or a relay switch or a malfunctioning thermostat that needs replacement. You should consult an HVAC professional.


Clanking may result from loose parts. It may also be a sign that the blades of the outdoor condenser fan or indoor fan aren’t balanced, which means they are hitting against other components as your air conditioner runs. You’ll need to call an HVAC technician to make the necessary repairs.


A broken or loose part may make a banging noise. This AC noise is often caused by a completely separated or loose crankshaft, piston pin, or connecting rod. When you hear banging sounds, it’s recommended that you turn your air conditioner off and wait for a technician.


Squealing sounds produced after you first start your AC system usually last only about 15 seconds. High-pitched squealing from inside your compressor could indicate dangerous operating conditions that need to be fixed immediately. A squealing sound when your system is running could be due to an old belt that’s loose or has slipped out of position.

Hissing Noise

A hissing sound typically signals a refrigerant leak and is one of the more common AC noises. The refrigerant makes the hissing noise as it escapes from cracks within your system. Refrigerant is toxic. Therefore, only a licensed professional should fix the leak.

Identifying strange AC noises and quickly taking action will help you avoid the need for financially devastating repairs or replacements. Contact us at NisAir Air Conditioning and Heating if you need assistance with any AC noises or issues in Martin, Palm Beach, or Indian River counties.

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