Are you sure you are talking about the "battery cutoff switch"? This switch is usually located in your battery compartment and is exactly like ones used in boats. The switch inside the door (usually referred to as the "salesman switch") controls only certain 12 volt circuits in the coach. It is so named because the salesperson can just hit the switch when coming or going and reduce 12v battery requirements.
Most of us do not need this switch and we bypass the relay it controls by jumpering the terminals. That way we don't have to worry about this switch breaking at a bad time.