Broken temp sensor or gauge?
 

which is more likely??

I thought my jag was overheating YET AGAIN but with the peg above the N I'm reading 160 degrees as my highest temp with a gun.

My findings over a few years with these beasts.

1) Temp sender unit.

2) The dash unit. Test that by earthing the wire at the sender, the gauge "should" go full scale.

3) The earth of the instrument pack is not as good as it should be, well documented.