Ice Cream Melting...

Please Help, Our "new" Kenmore (purchased October, 2004) Trio Bottom Freezer Refrigerator, Model 596.75509400, Serial 10890213ET, started making a different noise about two weeks ago. In the freezer, the ice cream got all runny, and the frozen French fries were soft (both items located in top shelf). The items in the bottom shelf seemed to still be frozen (fish fillets and steaks for example). The temperature in the refrigerator seemed to be about right. The intermittent noise, when it occurs, takes place every 2 to 5 minutes, for 3 or more times, started with a click, continues as a buzz for about 5 seconds, and concludes with a click. It sounds like something trying to start and then giving up. We pulled out the fridge, unplugged unit (condenser fan running), and made sure the lower area was free of dust. Although minimal, we blew out and cleaned everything, taking about 20 minutes. Upon plugging the unit back in, everything seemed fine for a couple of days (freezer at 0 degrees). Upon next occurrence (freezer at 30 degrees), we turned up the controls for both freezer and fridge (5 to 7), which seemed to work again (freezer at -15 degrees). After a couple of days, I turned the controls back to 5, their normal settings. After a couple of hours, it was off to the races again! The repair man arrived the next day, open the freezer, which was working fine at that moment, mentioned he had a lot of problems with the evaporator fan going bad, and walked out with a check. The next day he installed the new fan (by the way, I noticed ice on the evaporator when he removed the rear panel in the freezer), and walked out with a second check. The fix lasted about 2 hours. Upon calling the repair man again, explaining that his fix did not work, and going over our problem again in detail. He mentioned a relay, said he would be out tomorrow, and was never heard from again. Is there something I can do to fix this problem (9 days before someone from Sears can get out here)? Is the frost on the evaporator a clue to the problem, or a sign of impending failure? Any comments or advice would be greatly appreciated... Balto Marty