At home I have a GE Monogram ZIS480D about 7 years old, 3 weeks ago I noticed the compressor running constantly, and tried to lower the temperatures to see if it woudl cylce normaly but it did not, temperature at the time was -18C freezer and +3 Fresh food, about a week ago the fresh food compartment started to rise its temperature about a centigrade a day going up to +9C on the day I decided to take the refrigerator apart.
I started to see if the damper door did its job and it looks like it does, so I suspect that the evaporator is getting forzen, there is no acces to it but I see what looks like a suction line frozen going to the compressor.
As I have another exact unit handy to take parts from (I bought it for parts heavily dented) I exchanged the main board, both thermistors in the fresh food compartment, one thermistor in the freezer section (I missed the one in the evaporator) and both dampers (upper and lower) Im waiting a couple of days to get it started again as I suspect that the evaporator is frozen so there is enough time to thaw any Ice leftover.
I just got my hands on the service manual and I will take a shot at the diagnostics at night, but any input will be welcome if someone knows what may be going on.
There is little more that I can do, I missed to change one thermistor at the evaporator because I did not gain acces to it, (dont know how) and there is the resistance element at the evaporator and fans (condenser and evaporator) that I did not change...
The compressor looks like its working fine but it will be very hard for me to get my hands on one 240V unit.. (I live outside the US) the refrigerator I have for parts does not have the compressor...