Why is my air conditioner making a humming noise?

If your air conditioner is humming, it may mean there is an electrical or mechanical problem. Take steps now to determine the issue with your air conditioner. 

Potential causes of your cooling system’s humming can include: 

  • The condenser fan motor on the unit could be unable to spin but still has power reaching it, creating resistance that produces a pronounced—and often loud—humming sound. 
  • There could be a mechanical or electrical breakdown with the contractor relay switch, the component responsible for starting the outside unit when the indoor temperature reaches the level where cooling is required. When the contractor fails, it can produce a humming sound. The switch can be found in the exterior condenser unit outside your home. 
  • The circuit breaker is overloaded – normally, your circuit breaker trips when it becomes overloaded. However, if the circuit breaker is malfunctioning and can’t, you might hear an electrical humming noise. 
  • Ice on condenser – if your unit freezes over, this can produce a loud humming or buzzing noise. If your air conditioner is frozen, there are a handful of other likely causes such as a refrigerant leak, clogged air filter or faulty blower motor. A broken blower motor will often create a humming or buzzing noise, and is located in your furnace. If the furnace is positioned near the exterior condenser, you might mistake the source of the humming noise. With the AC running, determine if the humming or buzzing is louder near the exterior condenser unit or the furnace. 
  • The AC Condenser Fan Motor is damaged – similar to the blower motor failing, a broken condenser fan motor can also create a humming noise when it fails. If the indoor blower is running but the fan is not turning, your fan motor may emit a loud buzz. Some people perceive this noise as more of a hum than a buzz. There can be multiple causes for a failure of this part including debris reaching the condenser, overgrowth around the unit, loose parts, etc. 
  • Loose components inside the air conditioner – Your HVAC system is an intricate machine with plenty of moving parts. Over time, it’s possible that a handful of parts came loose due to average wear and tear. A loose part can cause premature wear and loud noises, including a humming noise. 
  • Refrigerant pipes are vibrating – If your refrigerant lines are undercharged, it can cause vibration. This vibration may sometimes sound like a humming noise. There may be other causes for a vibrating refrigerant line, like an improperly mounted expansion valve. 

A humming sound is evidence that something inside your air conditioner is off and needs attention. Given the causes above, it’s helpful to find where the sound is coming from. Your whole HVAC system is interconnected. The air conditioner relies on adequate airflow to operate normally. Air blows through the air filter, and it’s the blower motor (located inside the furnace) that circulates air through the entire system to heat or cool your home. If the air filter is dirty, or the blower motor malfunctions, that can cause issues with your condenser unit located outside the home. 

Resolving the AC humming issue does best with a technician to perform a diagnostic assessment on the whole unit. This work should never be attempted by a homeowner, but only by a certified technician. Your HVAC system has hazardous refrigerants running through it that should be safely handled only by a professional. Electrical components to your system should never be adjusted by a novice because of the danger of electrocution. Homeowners are better served hiring an HVAC company to diagnose and repair their system if they notice any odd humming, whirring, or buzzing noises coming from their unit.  

If a component like the blower motor is damaged, it may be because your furnace is near the end of its life. The blower motor is not a component that needs to be replaced often. Working with Service Experts Heating, Air Conditioning & Plumbing, we will not only diagnose your problem and provide recommendations to resolve things as soon as possible, we’ll also inspect your HVAC system entirely. If your unit is better off replaced, we have affordable options with top tier service available through financing. We also have the Advantage program that will get you a new system for a low monthly rate. 

  • How to Choose a Suitable HVAC System

    When it comes to keeping your home comfortable year-round, nothing is more essential than picking out the right heating, ventilation and air conditioning (HVAC) system. This decision affects your daily comfort, monthly utility bills and overall home efficiency. Then again, with so many system... Continue reading

  • Year-End HVAC Maintenance Checklist

    Now that the air turns chilly, you know it’s time to get your home ready for the cooler months ahead. Your heating system is critical to maintaining a cozy, warm setting. A well-maintained furnace supplies the comfort you want while using a smaller amount of energy. Regular inspections also make... Continue reading

  • 2024 Furnace and Air Conditioning Trends

    In the ever-evolving world of home HVAC, keeping up with the latest HVAC trends is crucial for homeowners who want to enhance their home’s comfort and efficiency. As we move into 2024, the HVAC industry continues to innovate, bringing new technologies and trends aimed at changing how residents... Continue reading