papa45 wrote:
The RV isn't here right now, but when I was messing with it a couple days ago, it measured something close to 0, less than 0.1V, as I recall.
OK, we could assume that the switch is interrupting the power to the light and continue to diagnose from there but just to be on the safe side, check to see if there is continuity between the wire on the switch and ground. If there is no continuity, you can safely assume that there is an open between the switch and the source of power. If the switch is in a bedroom that is the farthest away from the distribution center, you can assume that power is coming from a circuit close to the switch. Check nearby light fixtures, 12 volt power ports or any other 12V circuits close to the switch. The assumption that the switch obtains power from a nearby 12V circuit would be reinforced if you have just one light circuit or just a couple 12V circuits in the distribution center. You may be able to eliminate 12V power circuits as culprits by identifying those that are powering a single device--pump, thermostat, water heater, etc.
If it proves impossible to find the open in the circuit, you may wish to fish a new wire between the switch and a good source of 12V.