I’ll pile on to what’s been said previously.
I wired in a relay to my rear facing squadrons to run on up fitter 6 + reverse. I got weather proof relays or relays with weather proof housing. It worked great until about the dozenth rain storm and one night I noticed my neighbor’s lawn lit up. I thought it was motion lights and didn’t think anything of it. This repeated over the course of a couple days and I noticed it again, realized it was the truck, found the rear facing squadrons proudly illuminating my neighbor’s half acre. puzzled, I cycled the relay and it went off. I made a note to check/replace the relay the upcoming weekend. Next morning, there they are again. I didn’t want to be blasting the drivers behind me, so I pulled power to the lights. Pulled the relay apart and the weather proof connectors were not. The relays was wet and had corroded connectors. it was on maybe... 2 months?
It was placed pretty high up near the bumper, the truck wasn’t submerged or anything. I wrapped the new assembly to keep the water intrusion down, and that’s done the trick well.