In a method for controlling at least one fan (13) for the regulation of the cooling demand of at least two cooling elements (12) included in a drill rig (1), the cooling demand of each one of the cooling elements (12) being determined, that the determined cooling demands are weighted together and that the fan (13) is controlled based on the weighting together. At least one cooling element is equipped with a safety thermostat, which, if required, prevents undercooling by the fact that the fluid in question is not allowed to circulate in this cooling element. Also described is a drill rig for the execution of the above-mentioned method.