Cooler temperature?

Mojen together, the radiator temperature indicator in my 9000er (BJ 97, 2.3 Turbo) is supposed to settle in the “middle of the field” according to the manual. But with my Saab the needle hardly moves at all (max. 5 – 10 mm from the bottom to the top). That was already from the beginning, the dealer thinks it is OK, the car has now 90,000km on it. Does anyone know the problem, or is it none at all? The cooler fan still starts, by the way, if I stand for example long in the traffic jam. Thanks already