1. Confirm the thermostat is actually calling for cool
It sounds too simple to matter, and it is the single most common cause of a service call that did not need to happen. Set the system to COOL and the fan to AUTO, then drop the setpoint at least four degrees below the current room temperature.
Fan set to ON instead of AUTO is worth special attention in Florida. It runs the blower continuously, which moves air over a coil that is not always cold — so the vents blow room-temperature air between cycles, and moisture that condensed on the coil gets blown back into the house as humidity. The house ends up warmer and stickier than it should be.
2. Pull the filter and look at it
A filter loaded with dust chokes airflow across the evaporator coil. Less air across the coil means less heat removed from the house, and in bad cases the coil drops below freezing and ices over — at which point cooling stops almost entirely.
If the filter is grey and matted, replace it and give the system an hour. If you find ice on the copper lines or the indoor coil, shut cooling off at the thermostat, leave the fan running to thaw it, and read our guide on a frozen AC before restarting.
3. Check both breakers — there are usually two
Most split systems are fed by two separate circuits: one for the indoor air handler and one for the outdoor condenser. If only the outdoor breaker has tripped, the indoor blower keeps running and blowing air that never gets cooled. That is exactly the symptom you are describing.
Reset a tripped breaker once. If it trips again, stop. A breaker that trips repeatedly on an HVAC circuit usually means a failing compressor, a shorted capacitor, or a wiring fault — and repeatedly resetting it risks damage and fire.
4. Walk outside and watch the condenser
The outdoor unit should be running with the fan spinning and air blowing up and out the top. Three things to look for, from the safe side of the unit:
- Fan not spinning while the unit hums — commonly a failed capacitor or fan motor.
- Fan spinning but the air coming out feels cool rather than warm — the compressor is likely not running.
- Coil fins packed with grass clippings, dryer lint, or shrubbery growth — the unit cannot reject heat, so the house cannot cool.
Where the homeowner checklist ends
Everything above is visual and reversible. Past that point, diagnosing this fault properly means measuring: suction and liquid pressures, superheat and subcooling, compressor and fan amp draw against the nameplate, and static pressure across the coil. Those readings are what separate a $200 capacitor from a $2,400 compressor, and there is no way to guess them from the curb.
If the four checks above did not bring the temperature down, the next step is a measured diagnosis — with the price in writing before anything is replaced.
Want it measured instead of guessed?
The readings that settle this — pressures, superheat and subcooling, amp draw, static pressure — take a visit. You get the price in writing before anything is replaced.
(904) 467-1100