Short-circuit and open-circuit faultswere the two most common failure modes in electronic components；in most cases，a failed device manifests only one of two modes.This paper analyzes a solid-state relay（SSR） that exhibited both short-and open-circuit behavior simultaneously.Based on test results，failure investigations are conducted separately for each mode.The root cause is ultimately identified as a cold solder joint at the internal gate connection of the solid-state relay.This defect prevents proper gate drive and block the release of gate charge，resulting in both open-circuit and short-circuit phenomena.