Why does an AC unit freeze up?

An AC unit can freeze up due to low refrigerant levels, restricted airflow, or a malfunctioning thermostat. When the refrigerant levels are low, the coils can get too cold and freeze. Restricted airflow can prevent proper heat exchange, leading to ice buildup. A faulty thermostat may cause the unit to run continuously, causing the coils to freeze. Regular maintenance and proper airflow can help prevent this issue.