Method for operating an illumination device of a vehicle treatment system, which comprises a first thread having a number N of light modules that are connected in series, individually controllable and each equipped with at least one light element, and which comprises a second thread having a further number N' of light modules that are connected in series, individually controllable and each equipped with at least one light element, wherein the light modules (10, 12) are respectively connected within a thread by means of a circuit, characterised in that the method comprises the following steps: Detection of the configuration of the light modules (10, 12) of the first and the second thread, wherein the number of light modules (10, 12) of the first thread and the number of the light modules (10, 12) of the second thread are determined by means of the following method steps: - Successive supply of the light modules (10, 12) with a number Nmax ≥ N of different reference samples for the first thread and Nmax ≥ N' of different reference samples for the second thread, - Measuring an electrical parameter on the respective circuit in response to each of the reference samples, and - Analysing the measuring results of each reference sample and, from this, determining the total number N of light modules (10, 12) for the first thread and the total number N' for the second thread, and their respective operating state; and, when the number of light modules of the first thread and the number of light modules of the second thread are the same, the light modules (10, 12) of the first and the second thread are synchronously controlled when the illumination device is in operation and, when the number of light modules of one of the threads is greater than the number of the light modules of the other thread, the size and the position of a gap of the light modules of the other thread is determined, and, when the illumination device is in operation, the light modules (10, 12) of the first and the second thread are controlled depending on the determined size and the determined position of the gap and a light module of the one thread is allocated to each light module of the other thread in such a way that the light modules of the one thread which no light modules of the other thread have been allocated to are arranged in the region of the gap of the light modules of the other thread, and, when the illumination device is in operation, the light modules (10, 12) of the first and the second thread are controlled in such a way that light modules (10, 12), allocated to one another, of the one and the other thread simultaneously illuminate, and no light modules of the other thread illuminate, when the light modules of the one thread illuminate which no light modules of the other thread are allocated to. Detection of the configuration of the light modules (10, 12) of the first and the second thread, wherein the number of light modules (10, 12) of the first thread and the number of the light modules (10, 12) of the second thread are determined by means of the following method steps: - Successive supply of the light modules (10, 12) with a number Nmax ≥ N of different reference samples for the first thread and Nmax ≥ N' of different reference samples for the second thread, - Measuring an electrical parameter on the respective circuit in response to each of the reference samples, and - Analysing the measuring results of each reference sample and, from this, determining the total number N of light modules (10, 12) for the first thread and the total number N' for the second thread, and their respective operating state; and, - Successive supply of the light modules (10, 12) with a number Nmax ≥ N of different reference samples for the first thread and Nmax ≥ N' of different reference samples for the second thread, - Measuring an electrical parameter on the respective circuit in response to each of the reference samples, and - Analysing the measuring results of each reference sample and, from this, determining the total number N of light modules (10, 12) for the first thread and the total number N' for the second thread, and their respective operating state; and, when the number of light modules of the first thread and the number of light modules of the second thread are the same, the light modules (10, 12) of the first and the second thread are synchronously controlled when the illumination device is in operation and, when the number of light modules of one of the threads is greater than the number of the light modules of the other thread, the size and the position of a gap of the light modules of the other thread is determined, and, when the illumination device is in operation, the light modules (10, 12) of the first and the second thread are controlled depending on the determined size and the determined position of the gap and a light module of the one thread is allocated to each light module of the other thread in such a way that the light modules of the one thread which no light modules of the other thread have been allocated to are arranged in the region of the gap of the light modules of the other thread, and, when the illumination device is in operation, the light modules (10, 12) of the first and the second thread are controlled in such a way that light modules (10, 12), allocated to one another, of the one and the other thread simultaneously illuminate, and no light modules of the other thread illuminate, when the light modules of the one thread illuminate which no light modules of the other thread are allocated to.