This article was very helpful and I wanted to contribute my problem and how I resolved it.
attached is an illustration on how to trouble shoot whether to replace the PCB main board, Fan motor or just clear up the ice around the fan motor blade.
before you do anything I would recommend checking to see if you have ICE build up in the freezer, if so check If cold air comes out of the side duct (see jpg). if no air comes out you will have to remove all the trays from the freezer and remove the back cover carefully (you can flex the plastic to break it loose or just remove one of the rails) once you get the cover a little loose you will see on the left side the ice fan motor (unplug the two connectors red/white) remove the cover and check the fan blade to see if they are locked up with ICE) remove the ice check the blade can move freely.
remove all the ice from the freezer and reconnect the fan and put back the cover carefully. once you have done so plug in the unit and test if there is cold air coming from the top side duct. if you do get air you are done. no need to buy anything
if you don't get air you might will have to check the Main PCB by gaining access to the rear panel, once you have located the main PCB check the voltage like shown in the (JPG attached).
there is a trick to test this by putting the PCB in Test 1 mode (unplug the unit and plug and press the test mode button at the same time) then check the voltage. if you don't get 12 -16 volts you will need to replace the Main PCB. if you do get the correct voltage you will need to replace the ICE fan motor.
The part number for the fan motor is listed above is correct but be aware that depending on the serial number the main PCB might be different for example 708 Main Control Board p/n EBR34917104
I hope this helps