Few things are more frustrating than turning on your AC on a hot South Carolina afternoon and feeling warm air come out of the vents. Before you panic, know this: most of the common causes are fixable — and some you can check yourself in five minutes.
Check the Thermostat First
It sounds obvious, but the thermostat is the first place to look. Make sure it's set to "Cool" (not "Heat" or "Fan Only") and that the set temperature is lower than the current room temperature. Also check whether the fan is set to "Auto" or "On." If it's set to "On," the blower runs continuously — even when the system isn't actively cooling — which means you'll feel room-temperature air between cooling cycles.
If the thermostat looks correct and the system still isn't cooling, move on.
Dirty or Clogged Air Filter
A severely clogged air filter restricts airflow across the evaporator coil. When airflow is too low, the coil can't absorb heat effectively — and in some cases it freezes over entirely. A frozen coil produces little to no cooling.
Check your filter. If it's gray and matted with dust, replace it. After replacing, give the system 30–60 minutes to thaw if the coil was frozen before running it again.
Low Refrigerant (Freon)
Refrigerant is the substance that actually moves heat out of your home. If your system has a refrigerant leak, it loses the ability to cool effectively. Signs of low refrigerant include warm air from the vents, ice on the refrigerant lines or indoor coil, and a hissing or bubbling sound near the unit.
Refrigerant doesn't "run out" on its own — if it's low, there's a leak somewhere. Adding refrigerant without finding and fixing the leak is a temporary fix at best. A licensed technician needs to locate the leak, repair it, and recharge the system.
Tripped Circuit Breaker
Your AC system has two components: the indoor air handler and the outdoor condenser. They're often on separate breakers. If the outdoor unit's breaker trips, the indoor blower may still run — but it'll push uncooled air through the vents.
Check your electrical panel for any tripped breakers. Reset once. If it trips again immediately, don't keep resetting it — that's a sign of an electrical problem that needs professional attention.
Dirty Condenser Coils
The outdoor unit (condenser) releases the heat your system pulls from inside your home. If the condenser coils are caked with dirt, grass clippings, or debris, they can't release heat efficiently — and the system struggles to cool.
You can gently rinse the outside of the condenser with a garden hose (spray from the inside out if possible). For a thorough cleaning, a technician has the right tools and coil cleaner to do it properly without damaging the fins.
Frozen Evaporator Coil
If your indoor coil freezes, airflow through the system drops dramatically and you'll feel warm or barely cool air. Causes include low refrigerant, a dirty filter, or a malfunctioning blower motor.
If you suspect a frozen coil, turn the system off and let it thaw for a few hours with the fan running on "Fan Only." Then replace the filter and try again. If it freezes again, call a technician — there's an underlying issue that needs to be diagnosed.
When to Call a Technician
If you've checked the thermostat, replaced the filter, and reset the breaker and the system still isn't cooling — it's time to call. Refrigerant issues, electrical problems, and failing components all require a licensed HVAC technician to diagnose and repair safely.
Garris Air serves Spartanburg, Boiling Springs, Greer, and all of Upstate South Carolina. We'll diagnose the problem and give you an upfront price before any work begins.
Frequently Asked Questions
Can I add refrigerant myself?
No. Handling refrigerant requires an EPA 608 certification. More importantly, adding refrigerant without fixing the leak just delays the problem. A licensed technician needs to find and repair the leak first.
How long does it take for a frozen coil to thaw?
Usually 1–3 hours with the system off and the fan running on "Fan Only." Don't run the AC in cooling mode while the coil is frozen — it can damage the compressor.
My AC was working fine yesterday. Why is it blowing warm air today?
Sudden failures are often caused by a tripped breaker, a refrigerant leak that finally crossed a threshold, or a capacitor failure in the outdoor unit. A technician can usually diagnose this quickly.