Bev Air Kegerator conversion to Caskerator

I have decided to temporarily convert my Beverage Air kegerator for serving cask ale. To get the required ~55 degree temp - im going to use an external temp control box. This means the evaporator fan that normally runs continuously will now be cycled w the compressor. Im thinking this might not be a good idea. Any thoughts on what will happen? Will condensor coils freeze? I plan to only do this for a week at a time and during Boston winter months whe relative humidity is low. Any help appreciated.