Hi @lifelearner ,
The evaporator fan is a fan which draws air across the evaporator unit (which is normally freezing cold). It is located in the freezer compartment. This air is distributed throughout the fridge and freezer until the desired temp is reached.
It is not to be confused with the compressor fan which is located outside the fridge/freezer compartments and is designed to keep the compressor cool.
The evaporator fan turns off when the doors are opened as you don't want to blow the cold air out of the compartments. It turns back on again when the doors (both) are closed.
Here's a link showing the evaporator fan parts section (part #6 -11) of your fridge and its' location (roughly) in the freezer. It should be behind a back panel inside the freezer near to where you found the coils iced up. Once you've found the fan, either listen to it starting up or mark the blades to check if it has rotated after you close and open the doors (allow 10-15 seconds between close -open door to allow enough time for the fan to turn)
If the fan doesn't turn disconnect the power from the fridge and measure the fan motor using an Ohmmeter to see if it is OK. If it is reconnect the power and then use a Voltmeter to check if there is power being supplied to the fan. If you don't know how to do this then DON'T as there may be lethal voltages present.
If the fan rotates OK then you have to start checking the defrost heater part #7 in the parts diagram no.7. Here’s a link to the main page for parts for your fridge
Again disconnect the power and use an Ohmmeter to check the heater is OK.
Let us know how you get on.