Check your grounds
I wanted to post this with the hope that it may help others in the future. I purchased a used 2014 A.C.E. 29.2 with 3,500 miles on it out of Iowa a few months back. When I got it back to Chicago I found that the bedroom ceiling light and the courtesy light above the head of the bed did not work properly. They would come on but very dim. Also if the bedroom fan was on it would shut off when the wall switch for the ceiling light was activated. My experience with 12 volt told me to look towards the ground system. To make a long story short what I found was this. The rear shackle on the left rear spring was hitting a group of ground wires bolted to the frame near that location. Also the workmanship of the ground was questionable. It had star washers that were of the wrong size, it was very rusty and the wire loom was mounted in a way that did not keep it clear of the moving spring shackle. Re mounted loom and worked on the ground stud. Applied a product to improve and protect the ground wire connections. All lights and fan work fine since. I will redo all the chassis and coach grounds as I locate them.