Well nwjetboat as an actual owner verified but curious why p/o labled I looked at the manual which seems pretty clear, its simply a disconnect turning off campers access to battery(s). Why the p/o labeled as described is curious, in the off position, which I think you verified should be no 12v in camper. In the on position allows camper to use battery (and in your case truck battery). You need to add solinoid or other wise isolate truck starting batt. And use some alchol to remove label.
http://www.northwoodmfg.com/documentation/CAMPEROWNER%202004.pdf"You new truck camper is equipped with a 12-VOLT KILL SWITCH. The switch is located under the step to the bunk. The kill switch stops 12-volt power from the battery. To kill 12-volt power turn the
key until you can remove key. You may remove the key for security purposes, but it is not necessary to remove key to kill 12-volt power. Note that when the key is turned off or removed 12-volt power
will not be drained from the batteries–you need to turn the key on to operate with 12-volt power from the battery source.
The 12-volt kill switch should be used to avoid 12-volt drain if the unit is stored even for a short time period."
