Replaced both thermistors. Only the freezer side was bad, but since I had to remove the housing for the thermistor on the fridge side to replace the freezer thermistor I replaced both as a PM move. Works perfectly now. The video for this repair nails it, so watch it if you need to make this repair. ALSO - it is important to check for icing in the defroster catch pan and on the floor of the freezer. My pan was frozen solid with ice on the radiator, and a sheet of ice on the floor. The pan has a drain to the evaporation tray underneath the unit, and the drain was frozen solid, which caused the overflow. It is located at the bottom rear of the freezer behind the grill. I used a heat gun on low to loosen it up then just kept dumping hot water on the catch pan and poked a straightened-out coat hanger into the hole until it cleared. A bit messy but it worked. This took longer then the thermistor replacements!
This repair covers many models of Whirlpool (and their Kenmore badge) and Maytag side-by-sides. The fridge was about ten years old when the part failed. Expect the ice-maker and its sensors to also fail around the same time.. It was an even easier repair when I replaced them In January. Good luck.