An internal combustion engine provides mechanical torque and electrical energy for the operation of remote-controlled standstill air conditioning (remote start) in conventional vehicles. A new terminal is introduced for the remote start. A retrofit solution is offered for this terminal concept. A retrofit relay is provided which is plugged into a free relay receptacle of the motor vehicle. The retrofit relay has a contact which is connected to an output of a body control module which signals the receipt of a remote control command for initiating the “standstill air conditioning” operating state. The retrofit relay also has a contact which is connected to an output of a body control module which signals the receipt of an “ignition on” command for initiating the “driving mode” operating state. The retrofit relay includes a logic circuit which carries out a combination of the signals of the fourth and the fifth relay contacts.