ScottG wrote:
There are a bunch of them on eBay. Just search for RV led dimmer.
2 Wires?
Not so sure about that unless they are nothing more than a variable resistor.
DC electronics will need at least THREE WIRES in order to work.
Input + from battery
Battery "ground" (-)
Output + (variable 12V DC) to lights
Since OP has only 2 wires to work with they will most likely have to run a battery "ground" (-) to the switch location.
I suspect that the OPs wiring is only Battery + and the switched + that returns to the light fixture and no battery (-) to be had...