How to Wire a Mid-Trailer Turn Signal on a 24 Ft Haulmark Trailer Towed with a 2005 GMC Yukon XL

Updated 06/28/2011 | Published 06/25/2011

Question:

Why do the mid-trailer turn signal lights come on when I apply the brakes? What do I do to fix this problem? tow vehicel= 2005 GMC Yukon XL trailer= 24 ft. Haulmark

asked by: F. D

Expert Reply:

If the lights at the middle of your trailer are connected to the turn signal circuit then they will go solid when the brake lights are activated since trailers are wired with a two wire system. There really is no easy fix for this problem that I am aware of.

One option is to wire a connector with an extra circuit, if your Yukon has separate yellow turn signals at the rear, I believe most do, you could use a 5-Way connector set like the 5-Way Flat Trailer Wiring Kit, item # HM47890, and wire the extra blue wire directly into the turn signal only circuit that goes to the yellow turn signal bulbs. You would then need to run the blue wire on the trailer side to the lights you want to blink when the turn signals activated.

Normally, trailer side marker lights are only tapped into the taillight circuit, brown wire normally, for width and height identification at night and these lights are not used for turn and brake signals.

expert reply by: Robert G