Abstract: A process for controlling heat output of a heating device, such as an auxiliary heating device for a vehicle, and a switching arrangement for performing such process. The governing value in controlling the heat output is the temperature gradient with respect to time during heating of a heat exchange medium between two temperature threshold values. The threshold values are empirically determined and prespecified. The operating condition of the heating device is regulated in dependence upon the slope of the temperature gradient which is determined, preferably, based upon the time for heat-up of the heat exchange medium. The heat-up time is measured with the aid of a timer, and the heating time thus measured is compared with predetermined, prespecified values therefor.