Scott, I'm sorry you are having this problem with the refrigerator. A good check for this will be to first, try advancing it manually into a defrost cycle. To do this, turn the dial on the timer, clockwise very slow until it makes a loud click and the unit stops running. After a few minutes, if you can hear a sizzling or popping sound inside the freezer, it will mean the heater is on. In this case, the timer # 215846602 will need to be replaced. If nothing happens, I would recommend replacing both the heater # 5303918208 and bi-metal thermostat # 5303918202. If you would like more assistance, reply back with additional details and we will be glad to assist you further. I hope this will help you.