Same thing happened with me and was able to fix it by soldering the wires to the top 2 leads on the interconnect board. It is really difficult to do but I was able to complete it. Without the sensor mac mini just ran fan on high RPM so looks like it is used for whole system for temperature sensor.
Samsung Gear S2 3g Verizon uses following battery - Original Samsung Gear S2 Battery 300mAh (SM-R730A,SM-R735)
these instruction work only for 250 mah battery and version of the watch that supports it
Samsung Galaxy Gear s2 has 300mah battery and completely different
be careful when you order it.
also the screw driver Tool that iFix it for removing the back cover doesn’t work, it is way too big to get inside small holes