Temp Gauge Reads High All The Time - What's The Likely Problem?

A couple of friends nearby are restoring a '67 CJ-5 with the F134. As part of the restoration, they installed an NOS Speedometer cluster (which I believe came from DeBella).

The speedometer and the fuel gauge are both working fine, and everything appears to be wired properly. However, even when the engine is completely cold, as soon as the ignition switch is turned to the "on" position, the temp gauge immediately jumps all the way up to read High.

Thinking there might be a short of some kind, they replaced the wire from the gauge to the engine temp sending unit - and then even disconnected the sending unit entirely - but the result is still the same. When the ignition switch is turned to the on position, the temp gauge jumps straight to High.

Any thoughts as to the most likely issues that could cause this to happen? Is the (NOS) temp gauge itself potentially bad?

 

I'll just throw this out there
its a possibly the stud to sender is touching edge of housing

 

I believe twin2 has the answer. The temp gauge sender terminal would have to read a short to ground for full deflection of pointer. This has to happen between the gauge stud and the metal housing it is mounted in.

 

Thanks very much for these responses, and I forwarded them to the guys who are experiencing this problem.

If anyone else has any more ideas as to what may be the cause, please chime in!