Abstract: An arrangement for controlling the rotational speed of an output rotational part of a fluid friction coupling is provided. A fan for cooling components of a motor vehicle is coupled with a driving rotational part by way of a shearing fluid whose effective fluid quantity determines the transferrable torque. The arrangement contains an adjusting unit (which can be electrically driven in a timed manner) for the variable adjustment of the effective shearing fluid quantity and contains a temperature controller stage to which the temperature of at least one medium whose temperature can be influenced by the output rotational speed is fed. The invention, the temperature controller stage is followed by a rotational speed controller stage to which, on the input side, the output signal of the temperature controller stage is fed as the dessired rotational output speed as well as the rotational driving speed and which, via of its output signal, drives the shearing fluid quantity adjusting unit of the coupling.