I am a highly skilled appliance repair professional. I recently completed a job for a customer who was experiencing issues with their Kenmore refrigerator. The refrigerator was not cooling properly, and I identified the problem as a failed defrost thermostat. The defrost thermostat is responsible for regulating the evaporator defrost cycle, and when it fails, it can prevent the evaporator from properly defrosting, leading to poor cooling performance. To fix the issue, I removed the old defrost thermostat and replaced it with a new one. I also checked the evaporator fan and motor for any signs of damage or wear, and replaced them if necessary. After completing the repairs, the refrigerator started cooling properly again, and the customer was very satisfied with the results.