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The general test to find out if your defrost system is bad is to manually defrost the entire unit (24 hours). If the refrigertor works correctly when you turn it back on for the next couple of days (or weeks!). Then the problem is the defrost system.
It seems like he did this. There are a few components that this problem could point to in the defrost system. The board is generally the most expensive of the components that could cause this problem.
Please post the model number from the inside wall of the fresh food compartment so that we can see what you are looking at.
Did the refrigerator work correctly after it was defrosted?
Do you have ice and/or frost on the inside back wall of the freezer now? If not, have you checked behind the inside back wall of the freezer?
Can you feel any cool air coming in thru the vent from the freezer to the fresh food compartment?
The defrost thermostat (part 240 below) is a another component that may cause this problem.
Part 801 (below) is the main board that controls most functions (including the defrost cycle) on this refrigerator.
Let me know what you find and we can go on from the infromation that you have.