The invention relates to a device for detecting an electric arc in an electronic assembly, having: a transmission unit for generating an output signal, and an evaluation unit for receiving the output signal, where the transmission unit and the evaluation unit are connected to one another, where the transmission unit comprises an oscillator unit that generates an output signal having a frequency and/or an amplitude, and where the evaluation unit is configured to detect deviations, caused by an arc, in the output signal from the transmission unit. There is in particular a provision to implement the oscillator unit by way of a modified Pierce oscillator having an inverter, where the quartz is replaced by a detector coil. The invention furthermore relates to an electronic assembly of a motor vehicle having an apparatus to be controlled, in particular having a heating apparatus and having said device, and to a method for detecting an electric arc in an electronic assembly.