Why is my Hvac System Making a Loud Banging or Squealing Noise?

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Loud banging or squealing noises are clear signs your HVAC needs repair and should never be ignored. In our experience serving San Francisco homes since 1997, these sounds typically indicate mechanical issues that will worsen if left unaddressed.

Banging noises often point to loose or broken internal components. This could be caused by:

  • An unbalanced blower wheel or a loose connecting rod.
  • Debris trapped inside the indoor unit.
  • Ductwork expansion and contraction, which is common in older homes as metal warms and cools.

If these vibrations are ignored, they can stress the heat exchanger, potentially leading to dangerous carbon monoxide leaks.

Squealing noises are generally related to moving parts that lack proper lubrication or have worn down. Common causes include:

  • A worn blower belt slipping on its pulley (very common in older belt-driven blowers).
  • A failing motor bearing or a fan motor that has lost its lubrication.

If a squealing sound persists, the belt may break entirely or the motor could seize, turning a simple repair into a full motor replacement. If you hear these sounds, we recommend shutting down your system immediately and contacting us to schedule a professional inspection to protect your home and safety.

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