Running Lights Not Working on 2018 GMC Sierra With Roadmaster Diode 7-Wire to 6-Wire Wiring Kit

Published 11/22/2019

Products Featured in This Question

Roadmaster 4-Diode Universal Wiring Kit for Towed Vehicles - 7-Way to 6-Way Coiled Adapter Cord

(3413)

$160.90

Roadmaster Brite-Lite 3-to-2 Tail Light Converter for Towed Vehicles

(129)

$54.92

Question:

Im having an issue with hooking the diode tail light kit to a 2018 GMC Sierra with LED tail lights. the motorhome has a RM brite light 3-2 converter and the brake and turn signals work fine wiring per instructions, but even thou i have power for running lights they don't light up?? i was already 1200 miles into a trip across country before i realized i didn't have running lights. i rarely drive after dark or in adverse conditions, and when i do i have been using hazards while driving I would much rather be able to fix the issue.

asked by: Scott H

Expert Reply:

First of all, thank you for taking precautions to dinghy tow your 2018 GMC Sierra as safely as possible, and I think we can help you out with the issue you are having with the Roadmaster Diode 7-Wire to 6-Wire Flexo-Coil Wiring Kit # RM-15267 and Brite-Lite Wiring Converter # RM-732.

Based on what you said, since both your brake lights and turn signals are working fine, and only your running lights being problematic, I think we can easily narrow down the issue to a problem with the jumper wire between the diodes of the left and right tail light on your Sierra. What likely happened is that the wires were maybe not fully secured into the diodes for one reason or another, or the jumper wire was somehow crimped or damaged. This would really be the only reason that the running lights would not be functioning but the brake and turn signals would be so checking this should resolve the issue.

I have added a link to a help article on installing diodes on a dinghy with combined wiring that you also may want to check out.

expert reply by: Kyle S