The green light on a modern GFCI outlet is a function of its internal self-testing mechanism, which is often mandated by safety standards. This light signifies that the line side of the receptacle is energized and the GFCI's sensing circuitry is functional, meaning it can monitor. It is understandably confusing when a Ground Fault Circuit Interrupter (GFCI) outlet displays a green indicator light but fails to deliver power to a plugged-in device. The illuminated green light confirms the unit's internal electronics are receiving power and that the GFCI has passed its. The green light is on but there is no power? I reversed the wires and no light. I replaced it back with the old one and it works. I'm stumped and need some suggestions. Some GFCI also glows green light during a ground fault. In this article, I will explain what typically.