temperature gauge

I know that my clocks are a bit faulty including gauges, my temperature gauge is saying it is overheating. I just wanted to check that that the only place the car has a temp check is in the cooling tank? If so when I remove the connecter wires from the top of the tank the gauge should drop to nothing?

No the sensor in the expansion tank is for level, when you remove the wires the red LED in the guage should flash as if the water level had dropped too low.

The temp sender is located on the cylinder head outlet to the rad, its a small brass thing with I think a red/brown wire connected.