The present invention relates to a heating device for a motor vehicle with a dual-voltage vehicle electrical system. The heating device is operated with a power supply from the sub-system with the higher nominal voltage (for example 48 V), but actuated by a control device in the sub-system with the lower nominal voltage (for example 12 V). For this purpose, the heating device has a supply connection in the sub-system with the higher nominal voltage and a control connection in the sub-system with the lower nominal voltage. The control connection is disposed in particular on a control device which is integrated into the heating device and which is connected to a control connection of a switching element (power semiconductor) for controlling the heating device via a capacitive separating element in order to ensure potential isolation of the two sub-systems.