Existing vibration durability testing methods for a component is conservative in verifying the fatigue strength of a component. They more of typify the damaging potential of the real world vibration, instead of the component under test. This thesis proposes a new vibration durability testing method that works by giving emphasis to the dynamic behaviour of the component. From several tests carried out at different narrow frequency bands, it develops a diagram that shows the maximum limit of a component towards vibration. Design verification will then be made by comparing the result with the real world vibration. To this aim, a test has been carried out on a truck alternator at four different frequency regions and a vibration profile has been extracted by combining them together. Then, comparing the result with the real world vibration profile, the design of the alternator has been verified. Accordingly, the alternator shows less strength at low frequency regions.