I found a thread on your website that helped me here:
repairgarcia was having the same problem I was on a different fridge. The condenser is warm and there’s a line coming out that is cold. Frost is built up on the back of the freezer. I defrosted the back of my freezer with a hair dryer and it’s working fine now. What I need to find out is what part to replace. He was told to replace the heater. There are 2 heaters on your website and I’m not sure which one I need. Although the first one in the diagram looks like wires and a connector, but costs about the same.
part no. ap3708258 - def htr (no picture) or
part no. ap3183311 - heater & bracket asm
This is assuming the problem is not a sensor.
I should mention that the Freezer was not cold, but the fridge side seemed to be working fine.
Thanks for your help.