a sensor for monitoring the water content and the acid content in the presence of water in nonaqueous media can be incorporated into a monitoring system for monitoring the quality of nonaqueous fluids in equipment or vehicles . the sensor comprises an insulating substrate ; electrodes formed on the substrate in an interdigitated pattern ; and a conductive polymer deposited over the interdigitated electrodes which bridges between adjacent digits of the electrodes . the monitoring system incorporating the sensor comprises a control module for measuring the conductivity of the sensor . the control module is preprogrammed to compare the measured conductivity to a predetermined level indicative of an unacceptable level of degradation . the sensor is made by depositing electrodes on an insulating substrate ; depositing a conductive polymer over the electrodes in an amount sufficient to bridge between the electrodes ; and neutralizing the conductive polymer to an insulating form . a method of sensing water and acid in the presence of water in nonaqueous media exposes an insulating form of a conductive polymer to a nonaqueous medium and monitors the conductivity of said conductive polymer , as the nonaqueous medium is used . the conductive polymer reversibly increases conductivity in measurable amounts with increasing acid and / or water content due to protonation by the acid or hydration by the water .