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A humming air conditioner can be completely normal, as long as it’s making a steady, low sound. However, if any of your A/C components start to make a loud humming/buzzing noise, it’s more likely a warning of a problem within the system that an experienced HVAC pro should investigate further.

Common Causes of A/C Buzzing Sounds

A buzzing or alarmingly loud humming noise coming from your cooling system should be checked right away, because issues that produce this kind of sound can pose a safety risk, or damage/ruin your costly HVAC components if they’re not addressed promptly.

Buzzing can occur for reasons like the following, but regardless of the cause, it’s wise to shut your A/C down immediately and call for expert help:

    • Frozen cooling coil. Occasionally, your A/C’s evaporator coil might freeze up and produce a buzzing noise. After shutting down the system, put a container underneath the coil and let it defrost, then switch the power back on. If the coil ices up again, a pro needs to find out why.
    • Failed fan motor. A failed condenser or blower fan motor that needs replacement can start making a buzzing/humming sound if it’s seized up but is still getting power.
    • Bad contactor relay switch. If you hear loud buzzing at the outdoor unit and it’s originating from this low-voltage switch, the thermostat won’t be able to signal the unit to cycle on. Replacing the switch is usually a fairly easy fix that will restore your system’s cooling capabilities.
    • Loose wiring or electrical connections. Buzzing in any of the system’s electrical components is an indication of arcing. Electrical problems like this are a fire hazard, so they deserve prompt attention.
    • Malfunctioning circuit breakers. If the A/C breaker in your electrical panel is faulty and won’t trip, the overloaded circuit can produce a buzzing noise. This is a dangerous situation that needs to be dealt with immediately by a licensed professional.

If you have concerns about a humming air conditioner in your Martin, Palm Beach or Indian River County home, contact us at NisAir Air Conditioning and Heating for expert help.