In this paper, a technique for classifying the working condition of a water jet system is presented. The classifier is based on the discrete Fourier transform (DFT) of the electrical power signal. It is shown that this information can characterize the working condition of the system and predict the presence of (an incoming) faulty behavior. Experiments and comparisons with the 1-nearest-neighbor (1-NN) classifier have been carried out, showing promising results.