I have read several of the strings regarding Samsung fridges not cooling. Mine has froze up twice in the past 3 months. Power goes out quite often here so I wonder if that has anything to do with the issues. Anyway, the heater and lower thermistor tested out fine with multimeter according to specs of previous strings. My question is regarding the thermistor at the top (by the fridge light). Does this sensor have anything to do with the defrost cycle and should it be replaced?