Check circuit breaker #7 (middle row of CB's, 7th one down from the top) for 12v both sides. Relay K18 is the turn signal & brake lights relay (4th relay row from the top, far left relay) that should come from the exhaust brake system to the lights; also Relay K24 (bottom row of three, middle one) comes from the service brake side to the lights. Also Terminal Buss #1, 7th nut down is brake lights. I believe K19 (next to K18) takes a wire from K24 and K19 should be the Cruise Cancel Relay. If K24 is amiss, that may explain somethings.
See the Wiring Diagram I supplied to Coach Assist, page 5, but be advised that though the book was for an '06, the included diagram for brake lights was for '05's. Thus relay numbers are not written in stone. Click the blue link at the top of this page, and at the main BAC site, log in and find Coach Assist under the technical tab.
There should be a switch that the brake pedal interacts with, but others familiar with it will have to advise about that. In the past I've discovered such problems relate to the leaky lamp covers on the back of my coach. They don't seal out moisture or dirt very well, and every so often I have to remove them and clean out algae and gunk. Lamp contacts as a result may corrode and fail, often resulting in the whole system being out. So that would be my first place to check, but that's just me... no expert on complex 12v electricals. Check that corrosion, or a rock or something hasn't shorted out or disconnected a wire in the loom under the rear and at the hitch outlet. I'm disappointed that your entreaties to BCS went unanswered.
Joel
