Trailer Brake Problem..

whendrix13 · January 21, 2010

i have a 2003 gmc sierra Z71 and i put in a trailer in my truck. i got the harness from dealer ship and the controller from Napa. I wired it all up and well i ran in to this problem....

when i hit the slide button on the controller my parking lights(front and rear) come on. when my truck is running, i do the same thing and it doesn’t do it... I have trailer brakes, i know i do cuz i pull a trailer alot....

I asked to of my friends that have GM trucks and that both work at the chevy dealership and they said its wired wrong... i checked my wires and it was done right... Then one of them said to change a wire from the "A" spot to the "D" spot on the harness. i did that and the rear lights are the only thing that comes on.... im confused now... should this be happening??? Thanks in advance

BruceW · January 21, 2010

The brake controller should not control any external lights. It is wired incorrectly.

whendrix13 · January 21, 2010

its wired right.....

Red to red(stlt)

black to black(12v)

blue to blue(brake)

white to white) (ground)

thats how it is in my harness from the dealership and from the controller... its all stamped on all the wires where they go...

BruceW · January 21, 2010

The brake controller should tap into the brake light circuit to sense when the brake is applied. It has four wires. Typically they are blue for brake output, black for brake power input from battery, red for brake light circuit input and white for ground.

The only way I could see pressing the button on the brake controller lighting up anything would be if the blue brake output wire was connecting with a light circuit. The connection between the blue wire and the light circuit could occur anywhere in the vehicle. I suggest using a multimeter or test lamp to try to locate the fault.

csheatz · January 21, 2010

Using a test light or a muilti meter is the best way to solve this.

Also, if you press the button on the controler it should light up and your brake lights both truck and trailer should come on, same effect if you were to step on the brake pedal, without the truck brakes coming on.

I often use the button on my brake controler to back tailgaters off, or to turn the cruise off.