The center pin is for backup lights, and is only energized when you shift into reverse. For constant power, use the #4 pin (think "1 o'clock" position when looking at the outlet, "11 o'clock" when looking at the plug.)
Thanks for the reply. I have no power to the 1 oíclock pin which says battery charge. All others work fine as Iíve already wired towed vehicle. Fuse?
Depending on how your coach is wired, the #4 pin (12V power) might only be energized when the coach's engine is running. Again, depending how it's wired (RV manufacturers are famous for wonky wiring), there may be a fuse, probably in the big fuse/breaker block under the hood.