samsung freezer stopped working

I have a side by side samsung refrigerator freezer. It has a twin cooling system so independent for each. The refrigerator still works great. The freezer stopped working all of the sudden. I can hear the fan working inside of the freezer however when I open the door it slows down and dieS. The digital display is working properly and still displays the correct temperatures. I purchase the repair manual
however I do not know how to properly diagnose the problem. Any suggestions would be greatly appreciated. Thank you send mail