Plug in a suitable OBD reader (www.pscan.uk for an early car, any OBD2 for a later car) and see what temp the ECU is seeing.
the fan should come on at around 96'.
It should never get above 110..

Also unplug the coolant temp sensor and the ECU should run the radiator fan.

If the dash gauge goes over half way the engine is overheating.

Read More...