I only have the Varia radar without the light. Not quite sure I understand your whole thought process going on in the OP, but as ask by
Seattle Forrest why do you need the RDU? Everything will show or can be controlled on your Edge 830.
Perhaps the pairing for the light control on the 830 is separate from the pairing for the radar, or maybe you have to go in under that sensor on your 830 and enable that you do or don't want to control lighting with it.
As for the RDU, you'll have to read the manual.........
https://www8.garmin.com/manuals/webh...6_OM_EN-US.pdf