Why Does My Air Conditioning Hum?

Why Does My Air Conditioning HumTypically, your air conditioning system will make a slight humming sound while in use. It’s completely normal, for the most part. However, if you notice a distinct change in the tone or volume of the humming, it could be a condenser fan motor or contractor relay switch. Either one could be potentially problematic over time.

For the most part, the hum indicates the outside fan blade and motor are working as intended. At other times, the hum is an indication of a mechanical or electrical issue. If you’re unsure or notice a serious change, contact a local air conditioning technician.

A Loud Humming Noise

If your home’s air conditioning system starts to make a loud humming sound that seems irregular from its normal operation, it’s likely:

  • Condenser Fan Motor – The fan motor may have seized, though power is still working through the system. This seizure creates a resistance that produces the humming you hear.
  • Contactor Relay Switch – The relay switch is located on the exterior unit. If the switch fails mechanically or electrically, you’ll hear more of a murmuring sound coming from the unit.

Other Common Humming Causes

While the fan motor and relay switch are likely causes, they’re not the only causes of a humming sound coming from your HVAC.

  • Loose Wiring – If an electrical wire is loose or separating, an arc may create a noticeable buzzing sound.
  • Circuit Breakers – An overloaded circuit breaker feeding the air conditioning system may buzz if the flow is interrupted or halted whatsoever.

If you suspect a problem with your home’s air conditioning system, do not hesitate to call Metro Express Service. We proudly offer 24-hour emergency air conditioning repair.

Contact Metro Express Service at 817-516-0700 for top-rated HVAC repair, maintenance, and installation services in DFW!


Randy Murphy

Randy Murphy has been building his knowledge of the air conditioning and heating business for several years now. He first started applying his knowledge while working for his father’s HVAC company. Later, in 1987, Randy started his own business: Metro Express Service. He has been a top 10 Trane & Amana dealer for over eight years. When it comes to heating and cooling, Randy knows the business better than anyone.
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