Will AC freeze if it runs all day?

An air conditioner will not normally freeze simply from running all day long if the system is properly sized, well-maintained, and operating under ideal conditions with correct refrigerant levels and good airflow. Modern air conditioning systems are specifically designed to run continuously during peak summer heat waves to maintain comfortable indoor temperatures without forming ice on the coils. However, if your air conditioner runs all day and eventually freezes up, it is a definitive sign that a hidden underlying problem is hindering proper heat transfer within the equipment. Common triggers that cause continuous-running systems to freeze include severely clogged air filters, a slow refrigerant leak, a failing blower motor, or blocked return air vents that slowly starve the indoor coil of warm air over an extended period. If your system runs constantly without satisfying the thermostat, rather than blaming the duration of operation, you should investigate potential airflow restrictions or schedule a professional HVAC inspection to identify why the cooling capacity is compromised.