Evaporator fan not running

[WIRENUT71]

My freezer and fridge are not working properly, freezing the items in the bottom of each side but not cold up top. It is a GE side-by-side, about 30 years old. I don’t know the model # because the tag only has a JC Penney catalogue # and serial # and of course JC Penney corporate knows nothing about it. I replaced the evaporator fan because the old one was not working and while the new one does work it does not come on as often as it should. As a result I have stuff freezing about half-way up the freezer now and the fridge side semi-cold. The black wire that comes from the relay that goes to the fan had no voltage when I checked it but I don’t know when it should. When it does run it makes a loud buzzing sound. Also this model is too old to have a mother board. Thanks for any help!!!