Your A/C is running, the thermostat says 74, and the house still feels clammy. In South Florida that’s one of the most common comfort complaints — and it’s almost never about temperature. It’s about humidity, and a few specific things cause it.
1. The system is oversized
This is the big one. An A/C that’s too large for the house cools the air fast, then shuts off — before it has run long enough to pull the moisture out. That’s called short-cycling, and it leaves you with a cold, damp house. Bigger is not better down here. The fix starts with a proper Manual J load calculation so the system is sized to the house, not guessed from square footage.
2. The fan is set to ON instead of AUTO
Quick, free thing to check right now. If your thermostat fan is set to ON, the blower runs constantly — including when the compressor is off — and it re-evaporates the moisture sitting on the coil back into your house. Switch it to AUTO so the fan only runs while the system is actively cooling and dehumidifying.
3. Leaky return ducts
If your return ductwork leaks, it pulls hot, humid air straight out of the attic and mixes it into your supply. You pay to cool attic air, and the humidity never drops. Sealing or replacing bad ducts often does more for comfort than a new unit would.
4. It’s genuinely just very humid
Sometimes the equipment is fine and the load is just extreme — a lot of glass, a pool, high occupancy. In those cases a variable-speed system or a whole-home dehumidifier is the real answer, because it can run long, low, and dry without overcooling.
How we diagnose it
We don’t just swap the box. We check sizing, the fan setting, the ducts, and the actual humidity the system is holding, then tell you the smallest fix that solves it — which is sometimes free (the fan setting) and sometimes a duct repair rather than a whole new A/C system. If your house is cold but sticky, get a free assessment.