Sometimes the evaporator fan may get clogged with dirt and debris, slowing or stopping the fan as a result. Disconnect power to the refrigerator then remove the panel that covers the fan on the back of the refrigerator above the evaporator coils. Clean away any dirt and debris with a soft brush, replace the panel then reconnect power to the refrigerator.
The evaporator fan motor may start to fail over time, which will cause the evaporator fan to fail as well. To determine if this is the problem, open the freezer door and press on any of the fan or light switches. If the fan noise gets louder when the switch is depressed, the evaporator fan motor is the problem and will need to be replaced. Contact the refrigerator manufacturer or an authorized service technician for assistance.
If the refrigerator motor does not have enough voltage but the compressor and the condenser motor are both still running, the defrost control board will fail. The defrost control board controls the voltage to the fan motor, and the control board will need to be replaced before the evaporator fan will resume normal operation.
Another potential reason why the evaporator fan is not working is a failure within the defrost system, whether the timer, thermostat or heater. If the fan is not working and the automatic defrost system is not running at least once during a 24-hour period, the defrost system may be the problem. Contact an authorized service technician for assistance.