The series of work introduced in this paper is originated from a structural failure of the vehicle A/C (Air-Conditioner) pipe, and when many possible factors having been excluded, the main investigating endeavor is focused on RLD acquisition and analysis, which eventually leads to the successful design improvement.During this process, many important signal collectives, such as micro-strains, accelerations, and engine speed are provided by RLD acquisition in some predefined conditions. Subsequently, these signals are analyzed both in time and frequency domain. Furthermore, order analysis by correlation of acceleration and engine speed is also performed to find a definite reason.As a conclusion, the root cause to the crack is not excitation from the road, but mainly from the engine. Based on this conclusion, structure design is improved and is theoretically proved to be effective by the RLD comparison analysis. And the quantified validation to this work is given by the real road test finally.