An air conditioner should run quietly in the background. When it starts making noise you have not heard before, that is usually the system telling you something specific. Here is a guide to the most common sounds and what they typically point to.
Banging or clanking
This is often a loose or broken part inside the compressor, most commonly a connecting rod, piston pin, or crankshaft. It can also mean a piece of debris has gotten into the outdoor unit. Either way, this is a call now situation. Running the system with a banging compressor can turn a repair into a replacement quickly.
Hissing or whistling
A hissing sound can point to a refrigerant leak, especially if it is coming from the copper lines. It can also mean air is escaping through a small gap somewhere in the ductwork. A whistling sound at a vent usually means airflow is restricted, often by a dirty filter or a closed damper somewhere in the system.
Clicking
Some clicking is normal, a single click at startup and shutdown as the thermostat signals the system. Repeated or continuous clicking, especially if the unit is not turning on at all, usually points to a failing capacitor or a relay issue in the electrical control system.
Squealing or screeching
This almost always means a belt or motor bearing issue in the blower motor. It tends to get louder over time rather than going away on its own, and a failing blower motor can eventually stop moving air through the house entirely.
Buzzing
Buzzing can be electrical, loose parts vibrating against the cabinet, or in some cases a sign that the outdoor fan blades are hitting something. Electrical buzzing should always be treated as a priority since it can indicate a wiring issue.
Gurgling or bubbling
This is usually refrigerant related, air has gotten into the lines or there is a leak causing the refrigerant to boil at the wrong point in the cycle.
When to call right away versus when it can wait
Banging, electrical buzzing, and any burning smell mean shut the system off and call. Hissing, squealing, and gurgling should be looked at within a few days before they get worse. Occasional clicking at startup or shutdown is usually nothing to worry about.
If your system is making a sound that is not on this list, or you are not sure which category it falls into, it is always safer to have it looked at. A Kool Saver serves Miami Dade, Broward, and Palm Beach counties with same week appointments for most repair calls. Schedule a diagnostic visit or request a free quote.