Not defrosting/part of freezer is warm and part is cold

I have a Kenmore side by side refrigerator which was given to me a little while ago. The model number is 253.51232100 but I was unable to find anything about this model number even on the sears website. I talked to one of their parts people and they told me that in the future I could use model number 253.1232101 because it is the same.

Recently I our food started defrosting in the freezer and the refrigerator wasn't feeling as cold as it could. The bottom of the freezer was still very cold but not the top. I took off the back panel in the freezer in and saw a lot of ice build up completely covering the evaporator and the evaporator fan was not working. (the condenser/fan under the fridge seem to be working fine.)

So without knowing much about fridges I decided to replace the evaporator fan motor. After doing that I plugged everything back in and there was no change.

After reading a little on the internet I turned the knob in the fridge to force a defrost cycle. A little while later the heater element came on and then a while after that the evaporator fan turned on and ran for a couple of hours. Since this time (about a week) neither the heating element or the evaporator fan has turned back on. I have tried to force a defrost cycle again by turning the knob with a screwdriver until I hear a click but neither the fan nor the element turn on anymore.

Is this consistent with a bad defrost control board? But it seems like if that were the case then it should still defrost when I put it into manual defrost. It seems like the heating element and the defrost thermostat and the evaporator fan should all be working because they all turned on when I did the first manual defrost. But I'm not sure why they won't turn on when I do the manual defrost now. Unless of course I fried something by hooking up the defrost fan incorrectly.

Any advice would be helpful.

Thanks