Freezer works. Fridge is not getting cold ?
You will want to check the fan motor to see if it is running in the freezer compartment. If not then test it for 120 vac. If there is voltage the motor is bad, if not then the defrost timer is not sending power to the motor. Also check the evaporator coils to make sure that they are not clogged with ice and if so then it would be a defrost issue which you would test the defrost thermostat and heater for continuity. If no continuity then replace part needed. If there is then the defrost timer is bad and would need to be replaced.