When you stop and think about the main functions of an Air Conditioner, it becomes obvious how important air flow really is to the process of keeping the system from freezing up. With air flow that is constantly moving into the air intake, through the ducts, and eventually cooled by the coils, any obstruction that reduces this rate of flow may cause a potential freeze up. If air flow is reduced substantially, the warmer air we hope to cool will not be available to offset the coils refrigerant and it will get to cold and freeze.
One job our air conditioners do that we often forget is the removing of dust and particles in our living environment by simply moving air through the system itself. If you have ever changed your air filter, you will see that visible dust and dirt is evident after just a week or so of use. With this build up, the filters ability to breathe and allow air to flow properly becomes diminished and can lead in worst case scenarios to not only inefficiency but the freezing up of your system.
There are several other reasons you may experience problems with your cooling system freezing up but this is one you can check and possibly prevent yourself for very little money. For best performance it is recommended that monthly air filter changes be made especially in the months where the heaviest use occurs. Air filters are cheap, readily available at your local hardware store in all of the standard sizes and you can even inquire which type of air filter is right for your heating and cooling system here.