Need to find a live wire under dash of Chev class C

I found a stubbed out wire in front of the firewall which was triggered by reverse, I tied into that wire when I installed a backup camera and also tied into the camera lead with 12v power with a switch, in line, installed on dash. I utilized 1/4 amp diodes to keep from back powering the opposite lead that way the camera could be turned on when put in reverse, or I could switch it on to check the toad or traffic while going down the road. My Rig is a 2003 Fleetwood Storm, on a Workhorse P-30 chassis.