Ge Side By Side

The freezer side keeps frosting up.I have changed the defrost heater and the defrost thermostat. that did not work So i changed the main board/timer. that did not work either. I have tested everything again.
I have continuity at the heater and at the thermostat.froze or un froze.The heater looks like it has never been on. Were do I go from here.
Desperatly needs help The refrigerator is in the five to ten year range

My dryer (electric) belt broke and I’m trying to replace it, what I want to know is how do I take the shell off without destroying it to do so. I’ve never done this before.

never mind I figured it out