Can Trailer Wiring Harness Power Wire be Connected to Running Light Wire Instead of Battery

Published 07/23/2015

Products Featured in This Question

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(69)

$61.64

Starter Solenoid - SPST - 12 Volt - 100 Amp - Continuous Duty - Grounded

(14)

$36.08

Question:

Instead of running a power wire to battery and having it live all the time, why could I not Y into the running light wire at the tail light knowing that whenever I used the trailer I must have the tail lights on??

asked by: Peter C

Expert Reply:

When properly installed a powered wiring harness such as # 118460 will have power going to it all the time but not power coming out all the time because of the circuitry inside the converter box.

The tail light wiring on a vehicle is only rated for so much draw. By connecting the power wire to that circuit all of the trailer lights and vehicle running lights would be drawing on the one circuit and could overload it. Any deviations from the instructions would result in a void warranty as well.

I have included a link to a help article with tips on routing the power wire to the battery. It takes more time to run the power wire to the battery but the added circuit protection is well worth it. If you just want power off to the harness when the vehicle is off there is another option.

Instead of running the power wire directly to the battery you could run it to the output terminal on a battery isolator, # PK5231201. An input wire would then need to be ran from the positive battery terminal to the input terminal on the solenoid. And the 12 volt input will need to be wired to a circuit that only has power when the key is in the on position such as the radio. Turning off the vehicle removes power to the wiring harness in this set up.

expert reply by: Michael H