I Googled the make and model on internet and read several articles and video's and it was my opinion the problem was either the thermostat, or the the defrost heater. Many of these refrigerators also has a separate defrost timer but mine does not, I found out from the Appliance Parts Pro that mine is controlled by the main circuit board. I took a gamble and ordered both the thermostat and the heater and felt if this didn't fix it, then I would order the circuit board. After watching the video's I felt confident I could disassemble, defrost, and replace the parts, and I did. Very straight forward instructions and it took longer to defrost the coils than it did to replace the two parts. I'm guess 45 minutes to fix and replace the parts. Put it all back together and it works like new. Very satisfied at this point.