My refrigerator and freezer became warm yesterday. I unplugged the unit for 5 hours. Then I plugged it in overnight. The freezer made ice and the refrigerator was cool.

PROBLEM: I discovered the evaporator coils on the back freezer walls were frozen over and caked with ice. Also found a chunk of ice on the top of the coils. I unplugged the unit to let it thaw. Based on suggestions on this site, I also checked the following items:
1. Compressor is working
2. Condenser coils are clean (fronts were had lint on them but back was ok.
3. Condenser fan is spinning
4. Evaporator fan is spinning
5. Defrost Thermostat has continuity (got a reading of .4 on ohmn meter)
6. Defrost Heating Element has a continuity reading of 24.5
6. Defrost drain is clear, no pooling of water on floor of unit.

I don't know how to test for continuity on the evaporator fan motor but it does spin when the fridge is plugged in. Not sure what else to check. Would appreciate suggestions on how to proceed. thanks

Thank you very much for taking the time to respond to my question.
Can you tell me, is there a way to test my defrost timer to make sure it's bad?

Also, I watched the installation video for the timer and it discusses having to put the black wire on a certain terminal on the new timer. I don't have any wiring diagrams from my 25 year old refrigerator. Any chance you might know which terminal I should connect the black wire too? Thanks for your time and help.