Larry A Spring Valley , OH July 13, 2018 Appliance: KitchenAid Refrigerator KSSS42DBW00 Kitchenaid Refrigerator Ksss42dbw00: Defrost heater. How to replace Defrost Heater (Evaporator). I replaced the defrost heater element and the thermostat. There was nothing wrong with the thermostat, but I decided to replace it due to the age and location ( next to the defrost heater). 2 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 2+ hours