A/C Compressor Noise: What Does It Mean?

If your air conditioner is making unusual sounds, what you’re hearing could be an A/C compressor noise. The noises could mean that simple service and an adjustment are required, but they could also indicate that the compressor is about to give out. Here are some common A/C compressor noises and what they probably mean.

Just remember: you should call a qualified contractor for anything but the simplest problem.

  • Banging or clanking may indicate a loose internal part or mount. It may require a compressor replacement.
  • Bubbling (slow refrigerant leak) or hissing (catastrophic refrigerant leak) both require immediate attention from a qualified professional.
  • Buzzing could mean the motor is failing.
  • A chattering or rattling A/C compressor noise at start-up may diminish after 24 hours of power-on time. Give the air conditioner this time and see if the noise dissipates. If not, then the compressor should be replaced.
  • Clicking, rumbling, ticking or other noises at start-up could mean hardware in the compressor is loose.
  • Screaming may be caused by high internal pressure. If the system approaches a dangerous level, it should shut down automatically, but if you hear it screaming, shut if off immediately and seek service.
  • Humming, especially if the motor is slow to start, indicates that the starting capacitor could be going out. A steady hum during operation is a normal condition for all air conditioners.
  • Brief squealing at start-up is completely normal for some systems. However, if your compressor recently started making that noise, or it lasts well beyond start-up, the system requires attention.
  • Trumpeting A/C compressor noise at shutdown could mean an internal refrigerant valve is leaking. This isn’t a big enough problem to require attention unless hissing accompanies the trumpeting, or if there’s another problem with the air conditioner.

Clearly, there are plenty of A/C compressor noises your unit might make during its lifetime. Some are of immediate concern while others are completely normal. For questions about the noises your A/C is making, please contact us at Overland Park Heating & Cooling today. We’ve proudly served the Greater Kansas City area since 1983.

Our goal is to help educate our customers in Overland Park, Kansas about energy and home comfort issues (specific to HVAC systems). 

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