The inner guts section between the freezer and refrigerator compartments is freezing up into a solid block. This is causing frost and lots of condensation on the roof of the refrigerator and also the airflow is being affected. So the freezer won't freeze and the fridge just doesn't get as cool. I'm assuming its a sensor of some type. Is there a way to tell which sensor without shotgunning parts at it?

Thanks for any help.