Temp Guage issues

99% of gauges have 2 posts. The ones with 3 posts have the limiter housed inside. There isn't supposed to be a 12 volt wire to the gauge though. The wires attach to the printed circuit board. The 12 volt wire on your board very likely supplies both the limiter and the park brake indicator. That wire would be hot with switch on and probably not fused.
And we tear apart any gauge, especially when we have no spares.
They are quite fragile. I've received a few with feckin JB Weld all over them. Everything broken and worthless. Good luck through.