How to Use 4-Way Wiring of Trailer to Power Interior Lights from Battery

Question:

I want to take the four pin wiring harness from my trailer and connect it directly to a battery to power the interior lights when its not connected to a tow vehicle. How do I do this?

asked by: Mark G

Expert Reply:

You'll need to first convert the 4-way of your trailer to a 5-way since a 4-way does not carry an aux circuit that can be used for interior lights. If you were to wire the interior lights to 4-way wiring you'd end up having to have the exterior trailer lights powered at same time since it would have to be combined. So on the trailer end you'd want to install the part # HM47910 matching the current circuit colors with what you have now and then having the 5th pin run to the interior lights.

Then for battery you'd want to wire the 5-way part # HM47900 to it so that when you plug your trailer 5-way into it the interior lights would be powered. The jacketed white wire would got to the negative post of the battery and then the fifth circuit on the 5-way would go to the positive post.

expert reply by: Jameson C