It's not a sure thing, and I'm not sure if FR uses the same wiring schemes on all their RVs, but in my Rockwood there are several different wiring color combinations used for the 12V wiring. I have red/white, green/white, yellow/white, black/white, and blue/white 12V cables where the white is the negative conductor.
If you know what color wire you spliced into for the 12V, you can check at the Power Panel to see if that is the color wire attached to the fuse location.
In my RV there are several red/white and green/white pairs, so there are also several fuse locations with red and green wires attached.
2013 Rockwood 8289WS
Mods: Central Vac, PI EMS-HW50C, 2025RV, (2) SCS225 Trojans, PD9260, Awning Remotes & LED Lights, Eliminators, External Water Filter,, Intellijacks
2008 RAM 3500 Cab&Chassis Hauler Bed, B&W Companion Hitch
All My Modifications are at this link: