Circuit/System Description
WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
Battery positive voltage is supplied through a 40A fuse in the rear body wiring harness junction block to the rear defogger relay switched input. When the rear window defogger switch is pressed, the body control module commands the rear window defogger system by supplying voltage to the rear defogger relay coil. The rear defogger relay is energized and the defogger indicator is illuminated. With the relay energized, battery positive voltage is allowed from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger grid.