There is a refrigerant line running through there to prevent moisture from forming due to the temp. difference between the fresh food and freezer sections. It should be warm when fridge is running This line starts at the condenser , makes the loop and returns to the condenser It has hot refrigerant running through it. For it to get as hot as you say is not right. So - - go up on top and remove the panel to gain access to the refrigeration unit and check if the condenser coil is dirty and or the condenser fan is running. Problem there will make long run times and a hot mullion area. thanks for using justanswer.