Thank you for your question. It is concerning when the refrigerator is not functioning correctly. Samsung refrigerators are pretty straight forward to work on and have many automated test, to save you time. I will recommend you use only the forced mode to test the evaporator fan motor and the defrost heater circuit.
Some advice for you is when directions say 8-12 seconds, count one thousand one, two thousand two. In other words give it the full 8 to 12 seconds to enter the mode. The display will go blank and the refrigerator will beep during the entire test mode until taken out of the mode.
When you get the refrigerator into the forced mode press the FREEZER button once and only once,
This will turn on all the motors in the refrigerator. Use the diagram and a multimeter to check the voltage out to the evaporator fan.
Working with live electrical current can be very hazardous and possibly deadly. Testing voltage output requires working with electrical current. Do not attempt this measurement without the proper tools and safeguards. If you are not sure you can make these checks safely, please refer this work to a service tech.
Check on the CN75 connector the yellow to the grey. The reading should be 7-12 volts DC. Also on the CN 75 connector, check the black to the grey. There should be a volts DC reading there.
To go to the defrost heater test, press the FREEZER button once and only once. This is when already in the motor forced test and the heater will come on if the circuit is good. Measure on the CN 70 the brown to the red wire, there should be 120 volts AC. If there is 120 volts AC there and the heater is not on unplug from the wall and disconnect CN 70 from the board. Ohm out the circuit from connector CN 70, brown to orange with your meter. If you read 2600 ohms you have an open bimetal, defrost heater or themofuse.
If you read 47 or 47.5 ohms the circuit is good. If there is not 120 volt AC when measuring brown to red. Ohm out the thermistor circuit with CN 40 disconnected from the board the yellow wire, in the connector to the grey in on the CN 50 connector. Use the chart to find the resistance and compare to the temperature. Now what is the actual temperature? The thermistor is no more than a digital thermometer.
I will link you to the refrigerator on the website for parts . Samsung Refrigerator
If you have no time to check out the refrigerator here is a link for a Sears Home Services
technician to troubleshoot and repair the product.
I hope this is helpful. If I may be of further assistance please include more details in a reply below this entry.