The system is running. You can hear it. The thermostat says it should be cooling. But the house is not getting any cooler.
This is the single most common AC complaint in Florida, and the cause is usually one of five things.
Check these first (no tools needed)
Thermostat settings. It sounds obvious, but check the mode. If someone bumped it to "heat" or "fan only," the system will run without cooling. Set it to "cool," set the temperature a few degrees below the current room temperature, and wait five minutes.
Air filter. A clogged filter restricts airflow across the evaporator coil. Less air across the coil means less cooling into the house. Pull the filter out and hold it up to light. If you cannot see light through it, replace it. In Florida, filters need replacing every 30 to 60 days, not the 90 days printed on the packaging. Humidity accelerates buildup.
Vents and return grilles. Walk the house. Every supply vent should be open and unobstructed. Closed or blocked vents change the pressure balance in the duct system, and the rooms downstream of the blockage get warm air or no air at all. Check the return grille too. If furniture or a curtain is covering it, the system is starved for air.
Outdoor unit. Go outside and look at the condenser. The fan should be spinning. If it is not running at all, check the breaker and the disconnect box mounted on the wall near the unit. If the fan is running but the unit is buried in leaves, mulch, or hedge trimmings, clear at least two feet of space on all sides. The condenser rejects heat through those aluminum fins, and it cannot do that if the fins are blocked.
Causes that need a technician
Low refrigerant. Refrigerant does not get "used up." If the level is low, there is a leak somewhere in the line set, the coil, or a fitting. The system will run but cooling capacity drops steadily. You might notice the copper line at the outdoor unit is frosted or iced over. Do not add refrigerant yourself. A technician needs to find and repair the leak, then charge the system to the manufacturer's specification.
Frozen evaporator coil. If airflow is restricted (dirty filter, closed vents, failing blower motor) or refrigerant is low, the evaporator coil temperature drops below freezing and ice forms on it. Ice insulates the coil and blocks airflow further. The system runs but delivers warm air. Turn the system off and set the fan to "on" (not "auto") to let the coil thaw. This takes a few hours. If it freezes again after restarting, the underlying cause needs diagnosis.
Failing compressor or capacitor. The compressor is the pump that moves refrigerant through the system. If it is running but not compressing, the outdoor unit will hum and the fan will spin, but no heat transfer happens. A bad run capacitor can also prevent the compressor from starting. In either case, the system sounds normal but does nothing useful.
When to call
If you have checked the thermostat, replaced the filter, cleared the outdoor unit, and the house is still warm after 30 minutes, the problem is not something you can fix from inside the house. The most likely causes at that point are a refrigerant leak, a frozen coil, or a compressor issue.
Call (727) 477-3256. We are available 24 hours. If someone in the house is elderly, very young, or medically vulnerable, say so when you call.