Why Is My Air Conditioner Whistling?

Have you noticed a high-pitched whistling sound coming from your air vents? If so, you could be experiencing low return flow, which means that your return air vent is not getting enough air. As a result, your system’s blower is essentially starved for air, usually as a result of some type of blockage. This blockage produces higher pressure and air velocity inside of the vent, which in turn produces a whistling sound. Luckily, there are 5 common causes of air blockage that you can solve right away!


  • Dirty air filter: When filters become too saturated with dirt and debris, they can restrict airflow. Be sure to change your air filters every 3 months for best use.
  • Blocked/closed return or supply vents: If your return or supply vents are blocked (i.e. by furniture, pictures, etc.) then their airflow may be significantly reduced. Closed supply vents can also greatly diminish airflow. Make sure that all vents are open and that you remove any items that may be potentially blocking the vents.
  • Shut or partially closed dampers: Dampers are metal valves that can be closed to prevent air from being delivered to certain parts of your home. This can produce the same problem as closed air vents. To reinitiate air flow, simply locate the damper levels near the inside unit and make sure that they’re in line with the ductwork.
  • Large debris in ducts: Surprisingly, many small items can make their way through the supply vent gate into the supply vent, causing a blockage. If you suspect a toy, or other small item, may be lodged in your supply vent, remove the gate to check for and remove any foreign objects.
  • Too many closed doors: If too many doors are closed in your home, then the only path for air back to the return vent is via the small space underneath the door. This restricted flow forces the blower to work harder to retrieve the air, thus causing a whistling sound. Keeping doors open whenever possible will allow for better, more constant air flow.

If the above conventional fixes still leave you with a whistling Air Conditioner, it may be time to bring in an HVAC professional. Additional causes of a whistling Air Conditioner that can only be fixed by a certified expert, like General Air, include:

  • A return grille that is too small
  • A lack of return inlets
  • A malfunctioning blower
  • Leaky ducts
  • An oversized system

If you believe you are having a problem with your HVAC system, General Air is fully equipped to provide accurate assessments and recommendations, with full-service technicians to meet your repair or replacement needs. It is important to get your unit checked as soon as you notice a problem, so do not hesitate to contact General Air to get your heating and air systems operating smoothly again in no time.

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