BMW 320D cooling temperature E46

As it costs more to put on the temperature needle in the center of the scoreboard, I have changed the two grounds (motor block and EGR) and I see that it remains more or less the same.
Today I have made a journey of 70 km. Circulating by road at 2,000 rpm +/- The temperature on the hidden score marks me 71 or 72º, but if I reduce or accelerate moving from those revolutions immediately to 65º. Only step of that temperature at low revolutions when arriving in the city and stopping in a traffic light, but when returning to the normal march it falls again.

It gives me that to think that the fan (if it is viscous coupling, that I am not sure) is working all the time and that when the most rises of revolutions, it cool, it is reducing or accelerating, then you will have to check this "viscous coupling", what I do not understand is whether the thermostat of the block is closed as it manages to mark the temperature drop in the cylinder head if there is no step from the radiator. I suppose the thermostat is of the degree corresponding to the engine. If the fan is electric, it will be commanded by the ECU at the rate of the temperature probe (measure this) Another issue is whether the radiator carries and are open all the time ... Give us some detail of what this car has like this car. Greetings!!