I have a kenmore side. i have a kenmore side by side refrigerator from 1988 model number

Question

i have a kenmore side by side refrigerator from 1988 model number 3638597780 serial number b8512188. i dont know what the model is. it has 27 on the door handle. the back wall in the freezer will freeze to a block of ice. what is causing this. the food in the freezer is froze but the ice maker makes ice half the time. the refrigerator part is cool but not cold.