While all HVAC units are going to make noise when operating, new, unfamiliar noises could be a warning signal. However, sometimes these noises are actually coming from the ductwork, rather than the air conditioning unit. Some general noises and what they mean are further described below:
Buzzing - a buzzing noise likely indicates that there is an electrical issue in the condensing unit, often because there is poor electrical voltage moving throughout the system. More than likely this can be blamed on poor electrical connections or loose parts, but sometimes it can indicate that a compressor is failing. Because a compressor change-out is very expensive, all other components should be checked to prevent a misdiagnosis.
Clicking – Irregular clicking noises may be due to a bad relay, contactor, capacitor, thermostat or fan blade. While clicking is normal when a unit turns on and off, the noise should not be sporadic or constant while the unit is running.
Popping – A popping noise can either be indicative of a refrigerant issue or a ductwork issue. If it is coming from the refrigerant lines, then your unit could be sucking in liquid refrigerant through the compressor’s intake. This almost always results in serious damage; if you believe this is the problem, call a technician immediately. If the popping noise stems from the ductwork, it could be due to ductwork that is poorly shaped, sized or gauged. While the ductwork can be replaced in its entirety, it is far more practical to install duct liners, rubber pads (to prevent the duct from banging against surrounding objects), or fiberglass installation.