 Automotive vehicles and industrial applications employ numerous switches of various types. Even though today's switch detection systems apply a wetting current to burn off contact oxide, excessive contact resistance can still produce false detections. A methodology, using the existing features in a switch detection system, to validate the wetting current actually flows and to measure changes in contact resistance thereby providing the ability to monitor system health and develop a preventative maintenance schedule is presented.  A Diagnostic to Validate Wetting Current and Measure Switch Contact Resistance Degradation  