Michael M St Marys , GA March 31, 2015 Appliance: Kenmore Refrigerator 36358552890 Kenmore Refrigerator 36358552890: Not dsefrosting. How to replace Refrigerator Defrost Heater And Thermostat Assembly. Recognized problem freeze-over; seems to be the part isn't made very well or made to burn out: the defrost heater bulb. Replaced it and reefer works fine again. Do-It-Yourself Rating: Repair Time Estimate: 15-30 minutes