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 identify the issue with your air conditioner. 

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

  • The condenser fan motor on the unit may be unable to spin but still has power reaching it, creating resistance that results in a pronounced—and often loud—humming sound. 
  • There could be a mechanical or electrical failure with the contractor relay switch, which is responsible for starting the outside unit when the indoor temperature arrives at the level where cooling is required. When the contractor fails, it can produce a humming sound. The switch is located in the exterior condenser unit outside your home. 
  • The circuit breaker is overloaded – normally, your circuit breaker trips if it becomes overloaded. However, if the circuit breaker is broken and can’t, you can hear an electrical humming noise. 
  • Ice on condenser – if your unit freezes over, this can cause a loud humming or buzzing noise. If your air conditioner is frozen, there are several other possible causes such as a refrigerant leak, clogged air filter or damaged blower motor. A broken blower motor will often create a humming or buzzing noise, and is located in your furnace. If the furnace is installed near the exterior condenser, you might mistake the source of the humming noise. With the AC running, check to see if the humming or buzzing is louder near the exterior condenser unit or the furnace. 
  • The AC Condenser Fan Motor is damaged – like the blower motor failing, a broken condenser fan motor can also cause a humming noise when it fails. If the indoor blower is working 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 a lot of moving parts. Over time, it’s possible that some parts broke loose due to typical wear and tear. A loose part may 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 will 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 a closer look. Given the causes above, it’s crucial to narrow down where the sound is coming from. Your entire HVAC system is interconnected. The air conditioner relies on adequate airflow to operate normally. Air passes through the air filter, and it’s the blower motor (located inside the furnace) that pushes air through the entire system to heat or cool your home. If the air filter is clogged, or the blower motor malfunctions, that can cause issues with your condenser unit located outside the home. 

Resolving the AC humming issue requires a technician to perform a diagnostic assessment on your whole unit. This work should never be completed by a homeowner, but only by a certified technician. Your HVAC system has hazardous refrigerants running through it that should be carefully handled only by a professional. Electrical components to your system should never be adjusted by a novice due to 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 broken, it may be because your furnace is near the end of its lifespan. The blower motor is not a component that needs to be replaced on a regular basis. Working with Stevenson Service Experts, we will not only diagnose your problem and offer recommendations to resolve things as soon as possible, we’ll also inspect your HVAC system as a whole. If your unit has to be 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. 

Savings For You

See All Offers Here >
Offer

$50 OFF ANY REPAIR

  • Save $50 on a Paid Service
  • Written 100% Satisfaction Guarantee
  • Plus, ask how to save an additional 15% and waive your trip charge!
print
Offer

MAKE NO PAYMENTS FOR 30 DAYS!

  • Upgrade to Worry-Free Comfort with the Advantage Program and make NO payments for 30 days!
print

© 2024 Service Experts, Service Experts Heating & Air Conditioning, and the Service Experts logo and design are registered trademarks of Service Experts LLC and used under license by SE Canada Inc. All Rights Reserved. *Not applicable to the Advantage Program. See your signed Advantage Program Agreement for full details and exclusions. 100% Satisfaction Guarantee is subject to certain restrictions and limitations as set forth in the applicable Terms and Conditions.