Bottom mount freezer. The freezer gets very cold but the evaporator fan never starts. I have tested fan motor leads for voltage and it was not getting power. Used ohms test on motor and it appears to be fine. Question : 1) when/how does the evaporator fan gets its power to start up and stop ? 2) could the thermostat be shot ? 3) Is there a main board on this model which may need to be replaced . If so , wher is it located ?