How to Troubleshoot & Replace Whirlpool AP6010293 / WP67001794 Defrost Heater (Evaporator)

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. 

Although I replaced the heater coil the root cause was the sensor on evaporator return copper tube. I ordered both parts and choose to test the heater coil first. To rest heater coil I had to remove coil in order to access connectors at each end to measure resistance. Due to the level of difficulty in removing coil,I choose to replace coil while I had it out. The sensor is a much easier repair. The online Videos would have been nice before I purchased parts. One of the videos (heater coil replacement) didn't represent the model I had but was general enough for me to understand the procedure. 

First I thawed the freezer in totality. Seemed like a good time to clean everything too, then in my research I determined it was either the defrost heater or the thermostat kit. I ordered both. In the mean-time the fridge would work ok, except it showed dashes at stopped working. I assumed it was probably due to my original issue. That happened a couple days after the initial thaw. I got the parts and put my fridge into diagnostic mode. I tested the thermostat and it did fail (in the cold setting).I started by replacing the thermostat, then waited till the next day (when everything was at the correct temp, tested it again and it passed! This allowed me to test the defrost heater in the diagnostic mode and it indeed worked! I could see it got very hot and tested by putting some water on it and heard the sizzle. All in all it was a relatively easy repair and I am happy to know more about my fridge. I am sending back the defrost heater. It is awesome that APP encourages this behavor so that you have the parts you might need when you are doing the repair job. I opted to not install the defrost heater because that looked like a pain (would realistically take 5-10 minutes, not too bad) compared to just the thermostat and I am happy I followed my intuition. 

Ordered the defrost thermostat kit along with the defrost heater. Watched both videos and it was exactly what was said. The hardest part was putting back the clips back onto the coils. So far so good, no snow. 

The thermostat we ordered fixed the problem. 

Presumed defrost system failure, but after manual defrost got clicking relay on restart = start relay failure. Nothing else indicated starter relay - no rattling debris, power through relay, etc. - but all is well after replacing the starter relay. Want to commend Appliance Parts Pros for their online resources AND, especially for their honest business practices - no inflated shipping charges and no restocking fees! Have not dealt with such an honest business in many years, online especially, but puts many brick & mortars to shame as well. Cannot say enough about how pleasant it was to deal with them! Can't say I look forward to next time, but if an appliance must fail, I will return! 

With a new heater evaporator. 

I replaced the heater , the control thermostat for the heater , and the motherboard. An electrical surge from the power company took down several components. Don't forget the surge protector!