A control device is provided for a refrigerant circuit of an air conditioner, divided by a compressor and a vent element into a high-pressure side and a low-pressure side. The control device includes a high-pressure-side control part and a low-pressure-side control part for controlling one or more controllable high-pressure-side or low-pressure-side system components. The two control parts are coupled with one another, with at least one influential parameter of one control part forming a coupling parameter that is coupled into the other control part as an influential parameter that is effective there as well. The control device is useful for carbon dioxide air conditioners of motor vehicles.