06/24/2026
Preventing a through-the-wall AC unit from freezing up comes down to maintaining consistent airflow and keeping the coils clean.
The leading causes of an AC freeze-up are usually a clogged air filter, restricted airflow, or low refrigerant levels.
These specific, actionable strategies can keep your wall AC running smoothly:
Clean or replace the air filter: A dirty filter blocks the airflow needed to absorb heat, causing the evaporator coils to get too cold and freeze. Check your filter every two to four weeks during the summer and wash or replace it.
(See the post on this page for directions on how to clean your filter)
Keep airflow unobstructed: Ensure no furniture, drapes, or debris are blocking the unit's intake and exhaust vents. Your AC needs to pull in and circulate room air continuously to prevent the coils from icing over.
*Remove any large items from the top of your refrigerator that may be blocking airflow!*
Avoid setting the temperature too low: Running your AC on the lowest setting when it's mild or very humid outside can cause the refrigerant in the coils to drop below freezing. Keep your thermostat set to a moderate level (e.g., 72–75°F in humid weather).
