Control device for a vehicle air-conditioning electric additional heating

The controller has a power supply cable, and a control cable which transmits a control signal to a regulator for regulating an auxiliary heater such that the power supply cable simultaneously serves as the control cable. The control signal has a rectangle-shaped course over a time (t), and an amplitude (A) with respect to a normal power supply-voltage (U +). The power supply cable is connected to the regulator. An independent claim is also included for a method of operating a controller for an electrical auxiliary heater.