With this information in mind the following are a few problems that can result in your air conditioner icing up:

1. Dirty filter.
To avoid this replace or clean your filter every couple of weeks of the cooling season. If a smoker do it every week. To clean filter remove from air conditioner, wet thoroughly, and lay in bottom of a sink.
2. Dirty or blocked cooling coil.
An air conditioner requires regular maintenance. Usually every two or three years. Every year would be best, but this can be costly unless you do it yourself. During cleaning the cooling coil should be degreased and washed to remove accumulated dirt and debris.
3. Dirty or blocked condenser coil.
The condenser coil is the one at the rear of the air conditioner. Its job is to dissipate the heat that is being removed from the room. Just like the cooling coil it too must be cleaned every few years.
4. Inefficient compressor.
As describe above an inefficient compressor can cause icing up. If the compressor is not able to pump the refrigerant properly the cooing coil may not get cold enough to shut off the cold control.

5. Cold control not shutting off.

If the cold control does not shut off the cooling coil surface temperature will drop below the room’s dew point and begin to refrigerate. This will allow ice to build up onto the cooling coil.