RV Electric - I am obviously a novice

Thanks for all the replies. There is a common thread to my problems/ignorance because I encountered issues previously when trying to wire LED lights under my awning. I tried to hook them into an existing light fixture on that side of the camper. The fixture had two wires - Black (hot) - and White (ground). When I wired the red from my LED light to the black, and the black from my LED light to the white - nothing. I thought the LED light was bad because the fixture bulb still worked, but not the LED?!. I then hooked the LED direct to the battery as a test - bingo, worked. I eventually abandoned wiring into the fixture (frustrated) and tied into some wiring near our RV stereo. LED works great This issue with the bed motor is the same deal. Whenever I try to tap into the white/black 12v wiring scenario, I fail. Obviously I am missing something.... And someone is likely going to have an answer to exposes me as the goofy novice I am :)