AC Not Removing Humidity
Quick Answer
If your home feels humid even when the AC is running, check your thermostat fan setting first - it should be on "AUTO" not "ON". Other common causes include an oversized AC unit, dirty coils, or low refrigerant. A properly working AC should maintain 30-50% indoor humidity.
Safe Checks You Can Do
- 1Set fan to AUTO - Running the fan continuously blows moisture back into your home from the wet evaporator coil.
- 2Replace air filter - A dirty filter reduces airflow, which decreases the coil's ability to remove moisture.
- 3Check condensate drain - A clogged drain can cause humidity problems. Locate the drain line near the indoor unit.
- 4Monitor run times - If the AC cycles on and off in less than 10 minutes, it's not running long enough to dehumidify.
Likely Causes
- Oversized AC unit
An oversized system cools quickly but cycles off before removing enough moisture. This is a design/installation issue.
- Fan set to ON instead of AUTO
Running the fan continuously blows humid air back into your home between cooling cycles.
- Dirty evaporator coil
A dirty coil can't absorb moisture efficiently. Annual cleaning is recommended.
- Low refrigerant charge
Insufficient refrigerant reduces the coil's temperature and dehumidification ability.
- High outdoor humidity
In very humid climates, even a properly working AC may struggle. A dehumidifier may be needed.
When to Call a Pro
- Indoor humidity stays above 60% despite the AC running
- You've tried the fan AUTO setting and filter replacement
- You suspect the AC is oversized for your home
- You see mold or mildew growth in your home
- The evaporator coil looks dirty or frozen