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What a Humming Air Conditioner Means

Sometimes a humming air conditioner is one that’s working as it should, as long as the fan indoors and out are running simultaneously. But when the fans stop working and your house won’t cool, that humming could signal a problem that needs your attention.

If you hear humming from the circuit breaker box in your home, turn it off and call your HVAC contractor immediately. Circuit breakers that are overloaded will hum and if they get hot enough, will start an electrical fire.

Most of the time, the humming you hear will be from the outdoor condenser and it may be due to:

A Frozen A/C Unit

Before calling for service, check the condition of the air filter. If it’s clogged with dust, replace it and turn the system back on. If it looks good and you don’t see any frost inside the air handler, you may need to have an HVAC pro check the refrigerant level. Low refrigerant will freeze the evaporator coil, which can cause humming outdoors.

Condenser Fan Motor

If the blades aren’t turning, the motor for the condenser fan may be frozen. It will need replacing. Your home won’t cool as quickly and energy bills will rise. There could be compressor damage because the purpose of the fan is to blow off the heat the refrigerant collects from the indoor air.

Loose Wires

When two wires don’t connect tightly, you may hear humming air conditioner noises coming from one place. It’s best to shut it off immediately because loose wires get extremely hot and can start a fire.


The compressor is the loudest part of any A/C or heat pump, but when it just hums, there’s probably something serious going on. It might be complete failure or it could just be the rubber mounts, technically called isolation feet, that it sits on.

A humming air conditioner can happen anytime, including the hottest days of summer. To prevent the humming and the inconvenience and cost of a repair, contact Beyer Boys, providing trusted HVAC services for San Antonio homeowners.

Our goal is to help educate our customers in the greater San Antonio, Texas area about energy and home comfort issues (specific to HVAC systems).