An AC freezing up can result from restricted airflow due to dirty air filters or blocked vents, which prevents proper heat exchange. Low refrigerant levels caused by leaks can also lead to freezing. Other causes include malfunctioning thermostats, damaged blower fans, or faulty sensors. Regular maintenance, such as cleaning or replacing filters, checking refrigerant levels, and ensuring unobstructed airflow, can prevent this issue. If the problem persists, consult a professional to diagnose and fix the underlying cause.