Why Is My AC Running But Not Cooling?

The compressor is humming, the fan is spinning, but the air drifting out of the vents is room-temperature at best. It’s one of the most common calls we get during a Fort Mill summer. A few of these you can check yourself; others need a licensed tech. Here’s how to narrow it down.

Things you can check yourself

Thermostat settings

Sounds obvious, but confirm it’s set to “cool” (not just “fan”) and the temperature is set below the current room temperature. If the fan is set to “on” instead of “auto,” it’ll blow air even when the system isn’t actively cooling — which feels like warm air at the vents.

The air filter

A badly clogged filter restricts airflow enough to ice over the evaporator coil. If you see frost on the indoor unit or the refrigerant line, turn the system off, let it thaw for a few hours, and replace the filter. If it refreezes, that’s a sign of a deeper issue.

The outdoor unit

Walk outside and make sure the condenser is actually running and isn’t smothered in leaves or debris. If the fan isn’t spinning while the system calls for cooling, note that — it’s a useful clue for the tech.

The breaker

Some systems have separate breakers for the indoor and outdoor units. If the outdoor unit is dead, a tripped breaker is worth a look (though a breaker that trips repeatedly means stop and call a pro — don’t keep resetting it).

Things that need a technician

• Low refrigerant. If the system is low, there’s a leak — refrigerant doesn’t get “used up.” It needs to be found and sealed, not just topped off.
• A failed capacitor or contactor. These small electrical parts are a very common cause of a unit that hums but won’t cool properly.
• A failing compressor. The heart of the system; diagnosis and repair are a pro job.
• A frozen or dirty evaporator coil that keeps recurring after a filter change.

When to call

If the easy checks don’t restore cold air — or you spot ice, hear unusual noises, or smell something burning — it’s time for a professional. In peak summer, a no-cool problem only gets more uncomfortable the longer it waits. Our AC repair team offers same-day and 24/7 emergency service across Fort Mill, Tega Cay, Indian Land and nearby.