Common
You can check thisThermostat fan set to On
With the fan running nonstop, water that collected on the coil during a cooling cycle evaporates back into the house between cycles. Setting the fan to Auto is a free fix.
Routine
House feels humid even with the AC running
An air conditioner removes moisture only while its coil is cold and it runs long enough. Indoor humidity stays high when the system is oversized and runs in short bursts, when the fan is set to On and blows moisture back off the wet coil, when airflow is set too high for a humid climate, or when duct leaks pull in damp attic air. EPA guidance is to keep indoor humidity below 60 percent, ideally 30 to 50 percent.
- Florida-certifiedCAC1821225
- ServingBroward County · 14 cities
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The numbers worth knowing
An inexpensive hygrometer tells you more than how the house feels. These are what a humidity diagnosis looks at.
% RH
EPA advises keeping it below 60 percent, ideally between 30 and 50. Readings that stay above 60 in the afternoon mean the system isn't keeping up with moisture.
Auto / On
In hot, humid climates Florida's energy research center says to keep the fan on Auto. On re-evaporates water from the wet coil back into the house between cycles.
minutes per cycle
Moisture comes off the coil only once it has run for a while. Short cycles cool the air without drying it.
CFM
More air across the coil lowers how much moisture it removes, so blower settings matter for humidity as well as comfort.
Likely causes, most common first
Pick one to see how likely it is, who can deal with it, and what it means.
Common
Technician fixOversized system with short run times
A system that's too large satisfies the thermostat before it has run long enough to dehumidify. The air feels cool but damp.
Occasional
Technician fixReturn-side duct leaks pulling in attic air
A leak on the return side draws hot, humid attic air straight into the system. The AC then has to remove moisture it shouldn't be seeing.
Occasional
Technician fixBlower airflow set too high
Air moving too fast across the coil doesn't stay in contact long enough to give up its moisture. Blower speed can be set for better dehumidification.
Occasional
Technician fixDirty coil or low refrigerant charge
A coil that isn't cold enough, or is coated with dirt, removes less water. Low charge also means a leak.
Occasional
You can check thisLittle run time in mild weather or while away
In spring, fall or with the house closed up, the AC may barely run, so humidity climbs even though the temperature looks fine. Dedicated humidity control is designed for exactly this.
Where humid air gets in
Ductwork in a hot attic can pull outside moisture straight into the system.
When to stop and call
Turn the system off and call a technician if:
- Water is dripping from supply vents or ceiling grilles.
- The air handler closet has standing water or visible mold.
- Ceilings near vents are stained or sagging.
Checks you can safely do first
Tick them off as you go. None of them need tools or opening a panel.
Done all of these and it’s still not right?
That points to a part that needs a technician’s meter, not another reset.
Go deeper
- GuideRepair or Replace Your AC in South Florida?How to weigh repairing against replacing an air conditioner in South Florida, from age and refrigerant to repair history, comfort and matched systems.
- ExplainerAC Sizing and Manual J: Why Bigger Isn't BetterWhy an AC should be sized from a load calculation, not the old unit's tonnage, and why an oversized one leaves a South Florida house cold and clammy.
- ChecklistHumidity and Mold Control While You're AwayHow to leave a South Florida home for weeks or a whole season without coming back to musty air or mold, with AC settings, humidity targets and checks.
What our visit looks like
A technician measures indoor humidity and supply-air conditions, checks blower settings, airflow and refrigerant charge, times the system's cycles, and looks for return leaks in the attic. Then the technician explains whether settings, repairs or dedicated humidity control is the right answer. Free service call with repair.
Questions
Should my thermostat fan be on On or Auto?
Auto, for most South Florida homes. With the fan on Auto, it stops when cooling stops, so water on the coil drains away. On On, the fan blows over the wet coil between cycles and puts moisture back into the house.
What humidity should my house be in summer?
Below 60 percent, and ideally between 30 and 50 percent, which is the range EPA guidance recommends. In South Florida it's common to see readings in the 60s or higher when the AC is short cycling or the fan runs constantly. An inexpensive hygrometer will tell you where you stand.
Membership
Service Shield Protection Plan
- Two full maintenance visits a year, the same complete checklist each time
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- Up to 15% off repairs
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Florida license CAC1821225