If we're parked somewhere, and want the trailer running lights lit for safety/security, I added a switch within the trailer:
LIGHTED RUNNING LIGHT SWITCH: 12V DC (power and ground) were picked up from the outlet above the switch. The load conductor to the tail/running light circuit was connected to the green tail light circuit at a convenient location under the corner of the bed (above). Total additional load on the outlet circuit with the lights on is only about 3/4 amp. The switch should always be "off" when the umbilical is plugged in to the tow vehicle.
