In this study, we investigated the cause of the contact failure phenomenon of an oil temperature sensor whose signal error occurred intermittently as the vehicle in which it was installed was driving. The electrical contact failed sensor was disassembled and the contact surfaces observed with a scanning electron microscope (SEM). In this present oil temperature sensor, the difference in the thermal expansion coefficient of the male-female terminal and vibration during driving which arose when the vehicle was driven caused fretting corrosion at the contact area. The fretting corrosion caused an intermittent signal error. It is judged that the lead wire of the flexible thin plate is structurally vulnerable to vibration during driving, which further causes fretting of the contact point. Therefore, it is necessary to design an additional structural supplement to fix the flexible terminal of the sensor system.
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