Moisture

• One of the best known problems associated with the evaporator coil in a refrigerator's freezer compartment is excessive frosting and icing over. The coil is supposed to accumulate some frost, but an automatic defrost system in most models melts it away. Sometimes the frost will spread to the walls of the freezer and the evaporator coil will become covered in ice. This coating can drastically affect the cooling capacity of the fresh food compartment because airflow is restricted. Check the door gaskets to make sure there are no leaks caused by damage to the rubber.
  
  

Fan Motor

• All refrigerator evaporators have an evaporator fan. This fan pulls air across the chilled cooling coils and helps to create the chilly conditions that keep your perishable foods safe to eat. If the fan becomes noisy or stops working altogether, there may not be enough circulating cold air to accomplish this task. Symptoms that an evaporator fan is going out include loud chirping or squealing. You'll have to replace the fan motor to fix this. If the fan isn't coming on at all, then the motor has likely gone out already.
  
  

Defrost Components

• The defrost system is key in keeping the evaporator working efficiently. A thermostat tells a heater to turn on at regular intervals and a timer lets it know how long to stay on to melt the frost off the evaporator coil. If the heater isn't working correctly and is stuck in the on or off position, it could be because the heater or the timer have gone bad or the thermostat is malfunctioning. In any of the above situations, the frost will not be melted away and ice will continue to form on the coil.
  
  

Evaporator Drain Clog

• When the defrost system is working properly, the frost melts into water and it runs into a drain and is carried away to a pan in the bottom of the appliance to evaporate naturally. But if the evaporator's drain gets clogged, then the water has nowhere to go. The water backs up and eventually spills into the compartment below causing a mess. Ice, food or any other small foreign object in the drain will cause this. You will have to clear the drain and allow the water to escape normally to fix this.