Will an AC unit freeze up if low on freon?

Yes, an air conditioning unit will frequently freeze up and encase its indoor evaporator coils in a solid block of ice if it is operating with a low refrigerant charge. When refrigerant levels drop due to a leak, the pressure inside the evaporator coil decreases significantly, causing the boiling point of the remaining liquid refrigerant to plummet well below freezing temperatures. As warm indoor air is blown across this excessively cold coil by the indoor blower motor, the moisture condensing out of the air freezes instantly upon contact with the metal tubing, forming layers of ice that eventually block all airflow and shut down cooling performance. Running a system with frozen coils can cause severe liquid slugging and destroy the outdoor compressor. You can troubleshoot by turning off the AC and checking for ice. You can verify resolution when the coil melts completely and professional leak repairs are finished.