That's a slight bit confusing, pictures would definitely help, I can't imagine them wiring the AC into the dimmer switch? I do agree they might use the same power source, but they shouldn't have run the AC power through the switch. I have seen some goofy stuff in campers due to the Friday or Monday curse.
The white/purple and white run the AC when the white and white are together. So for some reason they are tied into the switch. A dealer finally found me the switch, $70 worth. I took the thing apart hoping to find some stamp or name so I could hunt one down. No luck but it does have a fuse in it and the fuse was blown.