It's July in Charleston. It's 95°F outside and your AC is running — but the air coming out of the vents is warm. Before you panic and assume the worst, walk through these six causes in order. Two of them you can fix yourself right now. The others need a pro, but knowing which one you're dealing with will save you time and money.
#1Low Refrigerant (Most Common Serious Cause)
Needs a proRefrigerant is the fluid that makes cooling possible. When there's a leak, refrigerant levels drop and the system can't absorb enough heat to cool the air. Signs include warm air from vents, ice on the refrigerant lines, a hissing sound near the outdoor unit, and rising energy bills. This requires a licensed technician — only certified professionals can handle refrigerant legally. The fix involves finding and sealing the leak, then recharging the system.
Learn about our AC repair service#2Frozen Evaporator Coils
DIY thaw, then pro checkThe evaporator coil sits inside the air handler and gets very cold as it absorbs heat from your air. If airflow is restricted (usually from a dirty filter) or refrigerant is low, the coil can freeze solid. Ice acts as insulation, blocking the heat exchange process entirely. Turn the system to FAN ONLY mode for 2–3 hours to thaw, check your filter, and if the problem recurs, call for service.
Schedule an AC diagnostic#3Dirty or Clogged Air Filter
DIY fixThe easiest fix on this list. A clogged filter starves your system of airflow, which triggers a chain reaction: the coil gets too cold and freezes, warm air starts coming through, and efficiency tanks. Charleston's humidity and pollen load means filters need replacing every 1–3 months. Check yours now — pull it out and hold it to a light. If you can't see light through it, replace it immediately.
#4Thermostat Issue or Wrong Setting
DIY fixBefore calling anyone, verify your thermostat is set to COOL (not HEAT or just FAN), that the temperature is set below the current room temperature, and that the display is active. If your thermostat is battery-powered, replace the batteries. Smart thermostats occasionally need to be reset after a power outage. This takes 2 minutes to check and is embarrassingly often the real culprit.
#5Failed Capacitor or Contactor
Needs a proThe capacitor starts and runs your compressor and fan motors. When it fails — and they fail frequently in Charleston's summer heat — the compressor may not start at all, or may run inefficiently. You'll often hear a humming or clicking from the outdoor unit. A failed contactor (the electrical switch that sends power to the compressor) produces similar symptoms. Both are relatively affordable repairs when caught early.
Our technicians carry these parts on every truck#6Compressor Failure
Major repair or replaceThe compressor is the heart of your AC system — and the most expensive component. A failing compressor may still run but not build enough pressure to cool effectively. If you hear grinding or clanking from the outdoor unit, or the unit is warm to the touch but the fan is running, the compressor may be failing. Compressor replacement is expensive ($800–$2,800) and on older systems, replacement of the full system often makes more financial sense.
Explore AC replacement optionsWhat To Check Before Calling
- Check the thermostat: Is it set to COOL? Is the set temperature below the current room temp?
- Check the air filter: Pull it out and hold it to a light. Replace it if clogged.
- Check the circuit breaker: A tripped breaker can cause partial failures.
- Look at the outdoor unit: Is the fan spinning? Is there ice on the refrigerant lines?
- Let it sit: After a power cycle or breaker reset, wait 5–10 minutes before expecting cooling.
If none of those quick checks resolve it, you likely need a refrigerant recharge, capacitor replacement, or deeper diagnostic. Our AC repair technicians carry common parts on every truck and can diagnose most problems in a single visit. We also offer 24/7 emergency service for true cooling emergencies.