MK4/B5/B5.5 Golf/Jetta/Passat OnStar harness to enable the red button backlighting and red indicator light (this can be removed if not wanting it to illuminate but retain the button lighting). Will not allow for use of the buttons but cavities for them are empty in the connector and can be repurposed for custom usage (they are variable resistance circuits, not individual momentary circuits but with modification or use of Arduino can be repurposed).
Simply splice into gray/blue dimmer switch wire and ground.