Jeffery K Overland Park , KS October 13, 2016 Appliance: General Electric Refrigerator ZIS42CMB Ge Refrigerator Zis42cmb: Refrigerator was not cooling and freezer was on ge built in. How to replace Defrost Thermostat. I called GE service and they did very little to test what was causing the problem. Instead, he indicated the damper was bad and the part was no longer available and I would need to replace. I purchased a defrost timer and defrost thermostat and replaced both. I am keeping my fingers crossed as now two nearly two weeks later it is working fine. This saved me plenty as a new unit can run $6k to $10K 1 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 30-60 minutes