In a previous post, Dirty Air Filters Can Cause Air Conditioners to Freeze Up we discussed the most basic parts and function of your Cooling System and how a very maintainable issue can stop the entire process. Basically the correct amount of warmer air flow is required to offset the cooling of the evaporator coil that transfers heat from the inside of your home to the outside. The condensation that is created in the process can freeze up around the coil if the warmer air flow is restricted or other problems exist.
If you are familiar with the basic design of the unit you can look to see if the coils are encased in ice to confirm the immediate issue. You may be able to remedy the situation with a few simple steps. The first thing you want to do is to turn off the unit and let it thaw out by simply turning the thermostat to off. Then look to see if the filter is dirty and replace it. A severely dirty filter can restrict air flow enough to cause a freeze up and it is the most simple thing to check. If it was a dirty turn the unit back on and the coils may thaw out with the better air flow.
If the issue persists there may be other contributing factors to consider which may include dirty coils or low refrigerant. Dirt coils are an issue as they may inhibit heat transfer and proper air flow to the cooler coils which are found inside the unit itself. Refrigerant issues are much more involved as they are under pressure and need to be checked using the right equipment. While the air filter may be something you can check yourself, we strongly recommend seeking the professional services of a NATE authorized contractor especially when dealing with regulated refrigerants.