DIAGNOSIS Ice buildup on the evaporator coils is caused by restricted airflow or a low ambient room temperature. The most common culprit is a dirty air filter.
FIX Turn the unit off and unplug it. Let the ice melt completely. This may take 24 hours. Clean the foam air filter as described in the filter Q&A. Ensure all air intake and exhaust vents are unobstructed. When restarting, set the thermostat to a higher temperature, not the lowest setting (60°F).
IF THAT DIDN'T WORK The refrigerant charge may be low, causing the coils to get too cold. This requires a professional technician to diagnose and repair any leaks before recharging.
HEADS UP Running the unit in Cool mode with a room temperature below 65°F can cause freezing. Use Fan mode only in cool ambient conditions.