Just recently the fridge section stopped getting cold. We manually defrosted for almost 2 days then everything started working again with no issues until someone turned the freezer control down one notch. A day afterwards I noticed an odor from freezer (thinking now it was food spoilage). Two days after everything in freezer had to be tossed as they were all defrosted.

Ever since, the temps in both freezer and fridge have been low. I do see frosting on the evaporator coils. I noticed by touch, something blocking the evaporator fan shortly after manually turning defrost timer. Would have to be ice buildup even though I don't visually see it. Although I have defrosted the fridge for 12 hrs. and the evaporator fan can be moved by my finger as a test, it would appear the evaporator fan either is too slow or just completely quit. I may have to change it. But I'm thinking I may have a defrost issue behind the fan. How can I troubleshoot it? I have a voltimeter.

This is a very old fridge, probably 1976, 1977 maybe? Model FPCI170T7 or FPCI-170T-7. I'm actually having issues with attempting to lift the evaporator coils to get to the evaporator fan. It is a bottom evaporator making it very difficult to get to the fan.