Adding Lights Inside Enclosed Trailer. Connect another length of wire to the other terminal of the switch also soldering that wire in place. If you are mounting your trailers lights to the bottom portion of your trailer on your pre-drilled light brackets be sure to clean the surface where you will be making your ground connection.
Turn signals and brake lights should be the brighter illumination and parking or clearance lights should be the dimmer illumination. The reason that your cabin light only goes on when your parking lights are on is because it is drawing power from the brown tail light power. If you have the factory set up it should have 12 volts at pin 4 only with the key on.
I got a 16x7 Aluma trailer and there 2 lights inside the trailer with switches.
Like theres no power to them The outside lights work. If you are looking at the truck trailer connector it. If you want a constant power source for your lights inside your trailer you would need to add a small fuse block under the hood run you a wire from the new fuse block to the rear wiring harness assuming there is an extra connection in the harness that is not being used and then run from the trailer harness on the trailer side through a switch to the lights you want to power. So the casing will help protect the light.