The central vac on my '77 is pretty much dead center on the rear wall of the bathroom. The switch to turn it on is just below the mirror to the left, over by the bathtub/shower. It looks like a standard household light switch, but it's mounted vertically with the switch hanging down from the overhead. Mine works like a champ. Kind of remarkable for being nearly thirty years old. I heard Airstream had some problems with them though. Seemed like a good idea to me though.