Both of the Freezer and the regular section are warm. We opened the freezer section, removed the back panel and found the evaporator coil was full of ice. I tried to search the forum and seems this is a common problem. Previous posts mentioned a sticky on GE for diagnostics of the defrost heater but I’m so sorry that I can’t find it. I’m hoping that someone can point me to the right direction so I can perform some basic diagnostics and order the right part.
Many thanks for the help.