bobk, this is calssic symptom of failed de-frost elements. This isn't as bad as it sounds though. After defrosting the ice build up, you'll notice that a few screws hold the back panel on to the fridge. You can remove these readily and the panel will then come off. This panel is very thin metal so try not to damage it when you remove it. (It will have a rubber or plastic gasket at each edge, don't damage this either). Once the panel is removed, you'll notice to electric bulb looking devices. They will be 4 to 6 inches long and about 1/2 to 3/4 inches in diameter. Failed ones (there are probably two) will look black. At any rate, these are not terribly expensive and can be picked up at any home improvement store or appliance store. Replace the them and reassemble. Best Luck!... (BTW, expect a lot of ice behind the referenced panel)