Bryan H Lake Zurich , IL January 09, 2016 Appliance: Whirlpool Refrigerator ET17JMXJW00 Whirlpool Refrigerator Et17jmxjw00: It wouldn't defrost automatically. How to replace Timer. I replaced the defrost timer after verifying the defrost thermostat and heater were good using a multimeter. 1 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: Less than 15 minutes