What Is That Noise? A Homeowner's Guide to Strange AC Sounds

Your air conditioner makes a certain amount of noise during normal operation. But when a new sound shows up, it is often an early warning. Catching problems early usually means a smaller repair bill.

Buzzing or humming

A buzz from the outdoor unit often points to an electrical issue such as a failing capacitor, a worn contactor, or a motor that is trying to start but cannot. If the outdoor unit is humming but the fan is not spinning, turn the system off and call for service.

Clicking

A single click when the system starts or stops is normal. Repeated clicking can point to a failing relay, thermostat problem, or electrical control issue.

Squealing or screeching

This usually means a motor bearing is wearing out in the indoor blower or outdoor fan motor. Older belt driven blowers can also squeal when the belt wears. Motors that squeal often fail soon after.

Grinding or scraping

Metal on metal sounds are serious. They can mean a failed motor bearing or a loose part hitting the fan blade. Shut the system off to prevent more damage.

Banging or clanking

Something may be loose, unbalanced, or broken inside the unit. In the outdoor unit, a loose fan blade or a compressor problem can cause banging.

Hissing or bubbling

Hissing can mean a refrigerant leak or a leaking duct. Bubbling or gurgling can mean a refrigerant issue or a partially clogged condensate line.

Rattling

Sticks, leaves, or debris in the outdoor unit, loose panels, or loose screws often cause rattling. Check that the area around your outdoor unit is clear, but leave the inside of the unit to a professional.

Loud air rushing from vents

This can mean your ducts are too small, your filter is too restrictive, or vents and returns are closed or blocked.

Our advice

When you hear a new noise, note when it happens and where it comes from. That information helps our technicians diagnose the problem faster. If it is grinding, banging, or a loud buzz with no fan movement, turn the system off and call us.

Red Rock Mechanical serves Oklahoma City, Shawnee, Bethel Acres, and Central Oklahoma. Call (405) 305-3085 or book online.