An alternator is subjected to large dynamic loads mainly because of vibrations on the engine and fixture type which affects the alternator’s lifetime significantly. A certain type of alternator had problems with its design, primarily as a result of damaged rectifiers caused by vibrations. To identify the reason of the failure, the experimental modal analysis (EMA) was performed on the rectifier. The main purpose of the experimental approach was to identify some of the design factors that shorten lifetime of rectifiers. The basis of the dynamic analysis were frequency response functions measured at the rectifier. Based on the measurement data of the original and modified samples of the rectifier, some corrections were suggested to improve the dynamic characteristics and to lengthen the lifetime of the rectifier. Useful information for the development of the next generation of the alternator’s rectifier was obtained. Applied methods can be extended to other products as well.