Current signature as a condition monitoring tool has a wide application to predict on–line motor related failures like broken or cracked rotor bars, rotor eccentricity, etc. A close study of its harmonics, specially distorted harmonics, can however lead to the prediction of drive problems which normally goes undetected when checked with normal electrical tools. In this papers through a case study, it has been shown that in a coal crusher plant a motor drawing overcurrent misleads the condition monitoring engineers to relate the same to mechanical fault of the coal crusher unit. Later stage after studying the distorted harmonics projected by the current signature analysis report lead to the fault of the variable speed motor drive.