I called about possible failure of components and was advised that the issue could be the defrost heater, thermostat, or timer. I was given the information to test existing components. The timer was not required in my unit. I tested the heater coil and thermostat. The thermostat did not pass testing specifications. Replacing the thermostat rectified the problem. Most of my time (two hours) was spent defrosting the evaporator coil so I could access the components for testing. Replacement of the thermostat and replacing all protective covers only took about 30 minutes. Appliance parts pros allowed return of unused purchased components. I paid for return shipping. Seemed fair to me.