David C Grapeland , TX July 12, 2017 Appliance: Frigidaire Refrigerator FRS20ZRGB2 Frigidaire Refrigerator Frs20zrgb2: Heater defrost not working. How to replace Defrost Heater (Evaporator). Replaced heater- defrost and while i was in there i replaced defrost timer for pennies. Do-It-Yourself Rating: Repair Time Estimate: 15-30 minutes