There is nothing connected to the Engine wiring from the RV coach systems. The ONLY possible item is the Ignition activated wire to the slide controller, but that would not affect the engine running or starting. What I WOULD suspect is, somehow the amp draw of the slide room caused a problem with the chassis battery. Either the battery is BAD and it is not supplying power to the chassis(which may cause an engine to die), or the fusible link that Chevy/Workhorse uses for certain chassis power is burnt. You stated engine will not start(GRRRRRRRRR), What the hell does that mean? Does it turn over? Does it turn over and not fire? Do you have any Dash lights that light up? Is the Dash Chassis system dead? Doug