Abstract: A process for activating a motor vehicle accessory (12), especially an auxiliary motor vehicle heater, and device for controlling the motor vehicle accessory (12) in which the activation commands for the motor vehicle accessory are input into a control part (10) which has control keys (11), an operating system, application software (16) which is specific to the activation of the motor vehicle accessory, a display (15) which also serves as an activation surface, and a data transmission interface (18), the activation commands are processed into activation data in the control part using the application software, the activation data are transmitted via the data transmission interface of the control part to the data transmission interface (21) of a base station (20) and are converted there into radio signals, the radio signals obtained in this way are output via a radio interface (22) and are transmitted to a radio remote control remote terminal (25) in the motor vehicle (13), and the motor vehicle accessory is ac

Abstract: An auxiliary motor vehicle heater (10) is provided with a control device (22) which has a connection (30) for a voltage supply line (32) which leads from the battery (34) of the motor vehicle to the control device (22). In order to especially more easily determine information for an auxiliary motor vehicle heater (10) about the operating state of the engine (36) of the motor vehicle, the control device (22) is set up to detect the voltage characteristic on the connection (30) and to determine the information “starting of the engine (36) of the motor vehicle is completed” depending on the voltage characteristic.