Temp gauge woes.. quick help needed

Right,
Temp gauge is refusing to work.
Changed the clocks. No difference.
So this must lead me to the sensor...
People have told me to earth it off and the gauge should read hot hot hot.. Ive tried earthing the wiring on the plug, and nothing happens.. although I am unsure what bit I am meant to earth?????
Is there a fuse/relay anywhere which could stop the temp gauge working? the rest of the clocks work.
If I have correctly earthed it off and it doesnt make the gauge work, then its the wiring. Can I bypass the plug for the loom in any way?
I have fitted another part of engine loom from a known working zetec fiesta, and made no difference.. so if its wiring, it will be from the plug on the bulkhead to the clocks,
If its possible to take one of the wires off the sensor plug to the clocks then I will try that,
Help needed asap as I could do with the temp gauge working!
