The rectifier serves as a critical element in water pumping systems, converting alternating current (AC) into direct current (DC) to power subsequent stages of operation. However, faults occurring in the associated measurement circuits, such as current or voltage sensing channels, can arise unpredictably, compromising control accuracy and potentially endangering system integrity. This study proposes a fault diagnosis strategy tailored to detect and distinguish between three prevalent fault types within measurement circuits: offset, scaling, and drift. The method facilitates both the localization of the faulty measurement path and the precise identification of the fault nature. Quantitative thresholds are established based on the observed influence of each fault type, and the technique operates without requiring additional sensors. A detailed dynamic model of the rectifier is developed to support the design of an estimator that computes residual signals under faulty conditions. These residuals are then processed to extract diagnostic features, which are subsequently interpreted by specialized functions for accurate fault detection and classification. Experimental validation confirms the effectiveness and reliability of the method.