Refrigerator section not cold, freezer section cold

Based on the relatively young age of refrigerator, I suspected the defroster electrical circuit. The evaporator core in the freezer was frozen solid, which confirms that the defrost heater circuit is not working. Thawed out (with a hot air gun) and disassembled the freezer section to access the evaporator core and defrost heater. If you have an ice maker, you will have to remove it to disassemble the freezer section. Confirmed with a voltmeter and ammeter that the defrost heater was not getting voltage. When the defrost heater is working, it will glow with an orange color. Also confirmed with a voltmeter that the defrost timer, located in the refrigerator section was working correctly. You can use a common blade screwdriver to rotate the timer through the cold and defrost cycles. Finally, I determined with a voltmeter and ammeter that the defrost thermostat, located on the evaporator core was not switching the defrost heater voltage. Ordered a new thermostat ($12) from this website and installed it. Refrigerator is as good as new. Be careful, there are many electrical hazards during the troubleshooting phase. Safety first.