Why do air conditioner coils ice up when the refrigerant is low?
Any refrigeration or AC evaporator coil has a tendency to ice up when they get cold. Water condenses on the coil when the air is cooled. That water can then freeze. If an AC system is operating correctly it will cool the air and eventually when room temperature reaches the set point the AC unit will turn off, this give any ice that has formed on the evaporator coil a chance to melt. If the system is low on charge, the room may never reach the set temperature and therefore will not shut off. The ice will continue to build on the evaporator coil until it is completely iced over. A dirty evaporator coil can cause this as well, so change your filters often. Another possibility is the ac system has to be matched to room or house size. Too small and too large a system will both cause you problems.
