When I bought my 2000 magna, the previous owner left his brake controller in the coach. The brake controller was mounted under the dash to the left of the steering wheel. The controller wiring cable goes through a hole drilled in the floor to the left and forward of the dimmer switch and passes into the compartment under the driver's seat. The control wire for the brakes goes through the bottom of that compartment and is run to the rear of the coach. It is then attached to a 7 pin connector that was added at the rear of the coach.
I haven't thoroughly checked the controller wiring cable but it appears the positive supply voltage comes from a wire run through the side of the front run 12 volt fuse panel.
2000 40' Magna #5892
Pete - Full Timing
2000 Country Coach Magna 40', CAT C10, #5892
2006 Jeep Liberty