Temp Gauge Help!!

[JoePolo]

So I am 80% sure I have a bad gauge. Fired up a truck that hasn’t run in a very long time. I had the cluster out at one point to repair blank/vacuum gauge hole and add a clock there since someone had killed the intermediate tin.
Temp gauge is pegged hot, I can see the needle. The sensor was not even hooked up at any time testing. I have not ohm gauged the sensor wire yet. I hooked up a ground to the gauge with alligator clips. All no change. And the gauge is pegged with the key off, so new gauge??? I have other clusters to steal a gauge out of, hoping I can do it from underneath, my seat it out and I would rather not pull the cluster again.