Temperature Gauge only slightly moves

I have a Rev5 MK2 MR2 and i find that the temperature gauge only slightly moves off the engine is up to temperature. Does anyone know how i can fix the problem so that it reads correctly.

First thought would be to confirm that it really is a gauge issue and not a faulty thermostat. The engine will still feel 'hot', its just not hot enough. See if the radiator top hose starts to warm quickly from a cold start (it should not because the 'stat should be closed'.

If it is a gauge issue then I guess the temperature sender on the block is the first suspect You might be able to find some data on what the hot and cold resistances are for the sender which is a thermistor, a resistor that varies its resistance with temperature.