My Fridge Compartment is not cooling, what's wrong?

Many modern fridges stop cooling in the fridge compartment due to an ice build up in the freezer. Frost free fridges make the cold air in the freezer and the air is blown down into the fridge. If the air flow is restriced by an ice build up the air ducts leading between the fridge and freezer compartments the fridge will become warm and eventually the freezer will stop cooling as well.