In the first two papers of this series, a complete algorithm was elaborated and tested for the diagnostics of vibrating control rods in pressurized water reactors (PWRs). Although the method was thoroughly tested in numerical experiments where even the effects of background noise were accounted for, the influence of the several approximations regarding the underlying neutron physical and mechanical model of the applicability of the method in real applications could not be properly estimated. In August 1985, in-core self-powered neutron detector spectra taken at Paks-2, a PWR in Hungary, indicated the presence of an excessively vibrating control rod. With these measured noise data as input, the previously reported localization algorithm was applied in its original form. The algorithm singled out one control rod out of the possible seven, and independent investigations performed before and during the subsequent refueling showed the correctness of the localization results. It is therefore concluded that, at least in this particular application, the approximations used in the model were allowable in a case of practical interest. The algorithm was developed further to facilitate the automatization and reliability of the localization procedure. These developments and the experiences in the application of the algorithm are reported in this paper.