Trailer Wiring Requirements for Using Multiple LED-Type Trailer Lights

Updated 09/20/2017 | Published 09/19/2017

Question:

I have an 18 ft enclosed trailer that I put 4 LED KC lights and 1 large LED light bar on, all lights wired in with the length of wire is to much of a load for the 12 volt feed, I am getting a voltage on the wire, 14 gauge wire is being used, I am thinking I need bigger wire but there is no way to connect bigger wire to the 7-way plug without issues. The 12 volt main going to the back of the factory plug is 6 gauge, how do I wire in a 6 gauge wire on the trailer plug and make all 5 lights work correctly?

asked by: Will

Expert Reply:

LED lights' advantages hinge on their high electrical efficiency, which is roughly 10-times that of standard bulbs. This efficiency typically means more light output for the available power level and reduced waste heat, along with the benefits of not having to replace bulbs, and not having to live with bulbs whose light output often turns yellowish as they age. LEDs are smaller, lighter and usually make your trailer easier to see.

Despite their efficiency, it is still certainly possible to install enough of these LED lights to overload a vehicle wiring harness' 12V trailer power feed. Without knowing your specific lights' total power demand, nor your vehicle, it is hard to say whether you really need heavier-gauge wiring. I do presume that all of these lights are being powered by the same 12V auxiliary power feed from the vehicle 7-way. This 12V auxiliary power is carried on the vehicle socket's 1-o-clock contact as shown in the linked article.

If some/all of the lights are not working you might have a ground issue more than a power issue. Using 14-gauge wire to power the LED lights ought to be plenty in most applications. 20-feet of 6-gauge wire can handle up to 100-amps of current! I do not know of any LED lights that are this power-hungry but I suppose it is possible. Whether the lights use a separate ground wire or a mounting stud to establish the ground you might try sanding off the grounding point for each light and/or at the main trailer ground on the frame.

You may also want to consider installing a separate battery on the trailer to power those lights. Trailer-mounted batteries can receive a maintenance-level trickle charge from the 7-way as you drive so that they remain topped off and ready for use.

expert reply by: Adam R