How to Troubleshoot & Replace Whirlpool AP6020675 / WPW10383615 Thermistor

Thaw evaporator (with heat gun) check other parts (wiring, heater, inline fuse) from disconnect Ordered part on line and arrived within a 24hr with standard shipping . This was great customer service. Then replaced evaporator thermistor (old read 6k and new 4k at room temp). 

We replaced the Thermistor and the Control Box. We decided to do both so we would have it working again without issue. It's possible we only needed to replace the Thermistor but seemed more worth it to just do both while we had it empty and open. I marked challenging below at 3 as it was easy to repair but diagnosis was more difficult. 

I used your troubling shooting guide and bought a defrost heating element. I checked it out with my volt meter and sure enough it was broke. I had also bought a thermistor but after about a week of no noise I sent it back to you guys. Thank you very much for your return policy. Two weeks later the Whirlpool started making the noise again and I order a thermistor from you again and installed it. So far so good. The job did not take long and the longest part was defrosting the ice to replace the parts. 

Replaced thermistors and freezer then went to -22 but ran continuously. Replaced the controller and freezer now running properly. 

Spoke with tech, explained issues. Tech suggested part and it worked. No issues 

I replaced both parts. Note: I feel the bad temp sensor was the cause of the evap fan burning out due to contined ice build up around the fan. 

I ordered a temp sensor that controls the defrosts the evaporator. I used a quarter-inch socket and ratchet plus Philips screwdriver. I had used my wife's hair blow dryer to defrost the evaporator coil, after all, it took me about an hour to complete. 

Replaced thermistor