Air ConditioningWhy Is My Air Conditioner Making Loud Noises?

Your air conditioner might be making loud noises because it’s time for maintenance. It’s not uncommon for A/C systems to make a variety of sounds. What’s most important is the type of sounds that your unit is making, since each sound can indicate a different issue. Here are some common reasons for a noisy A/C system:

#1 Squealing

If you hear a squealing or screeching noise coming from your air conditioning system, it’s most likely a result of problems with a belt, blower, or motor. While this isn’t hazardous, if left in poor condition, it can cause larger repairs later or even an immediate breakdown. For some systems, this sound is normal when you initially turn on the A/C. However, you should be able to tell if this is normal for your system or if there is an issue.

#2 – Chattering or Rattling

A rattling sound coming from the air conditioner could mean that the system itself may be starting to deteriorate and parts have become loose. The electrical contactor in the equipment can make a chattering sound as well, which can cause damage to other components including the compressor if the issue isn’t resolved. Another reason for the rattling sound could be the fan, which can rattle when it’s loose. This can be resolved by checking for loose screws or bolts in the A/C unit’s casing, clean condenser coils, and change your indoor air filter.

#3 – Whistling or Screaming

If you hear high-pitched whistling, shut the air conditioner off and call a professional right away. The most likely cause is a refrigerant leak, which not only damages your air conditioner but can also put your family’s health at risk. Screaming might also indicate high internal pressure within your compressor, can be dangerous. If your air conditioner turns off on its own, don’t worry. A sensor is doing its job to protect you from a potentially hazardous situation!

#4 – Buzzing

  • There is a problem with the electrical connections.
    Electrical connections will actually become loose over time and eventually make a humming noise. If the wiring isn’t repaired, your AC may start shorting your home’s power.
  • You may have an issue with your home’s circuit breakers.
    Failing circuit breakers will cause the outdoor unit to make this noise.
  • Your air conditioner has “frozen” overtime.
    If your AC frequently freezes, it’s important to figure out why and get it fixed. Possible reasons for this are restricted airflow or refrigerant leaks. It’s likely that you will see ice in or on the unit itself if freezing is the case.
  • The A/C condenser fan motor has stopped working.
    Your inside blower may be running, but if the outdoor unit’s condenser quits it can cause buzzing.
  • Your system’s contactor relay switch may have an issue.
    One of the more common reasons behind buzzing is also one of the least expensive to resolve. If the contactor relay switch has stopped functioning, that can be the culprit. This switch controls the flow of electricity to the compressor.

#5 – Humming

Humming generally isn’t serious, but it’s still indicative that something inside your A/C may have an issue. Loose parts and refrigerant piping can cause vibration and, if left unchecked, can lead to a more serious issue.  If the compressor hums and refuses to start, there may be an issue with the motor, though loose wiring could trigger this noise as well.

#6 – Thumping

This can occur in your system when things become caught in the fan. If you hear any loud thumping or banging, your initial thought before calling an HVAC professional should be to check your system for any trapped debris. This kind of sound can also be a sign of a loose or out-of-balance part or the indoor blower or outdoor fan and its blades are out of balance and hitting other parts.


Using an improperly-working air conditioner can lead to further damage, larger expenses, and safety issues. Keep in mind that repairing an A/C system and the electrical components they contain should always be left to HVAC professionals. If you hear any unfamiliar noise, shut the air conditioner off and call a professional right away. We can handle your air conditioning repair and maintenance needs. With our high-quality service, we’ll make sure your AC can effectively take on the summer heat. We serve the areas in and surrounding Seattle, Redmond, and Tacoma.

Call us at 425-533-9058, or use our Online Contact Form to arrange maintenance or repair service.


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