Where to Splice Brake Light Wire From Brake Controller To Stoplight Wire

Updated 05/31/2024 | Published 08/28/2015

Products Featured in This Question

Hook Probe Circuit Tester

(70)

$13.12

Quick Splices - Self-Stripping Connector - Closed Port - 14-16-18 Gauge - Blue - Qty 1

(65)

$2.85

Question:

on the brake pedal wiring which wire should the red wire for my controller be connected. My truck did not come with the pre wired plug?

asked by: BG

Expert Reply:

Since your vehicle does not have a brake controller port, you will want to use a universal wiring pigtail. For example, if you have a Tekonsha brake controller, you could use a Plug-In Harness for Tekonsha and Draw-Tite Brake Controllers # 20127. You will want to use a circuit tester, like # PTW2993, to test the wires at the stoplight switch at the back of your brake pedal to find the wire that only has signal when the brake pedal is depressed.

Once you have found the wire that only produces signal when the brake pedal is depressed, you will want to splice in your red wire from your brake controller harness. You can use a splice like the quick splice # SWC502905-1.

The red wire can be spliced with the stoplight wire at any spot in the wire, just be sure you will have enough wire to reach your brake controller.

I have attached a diagram on splicing in a brake controller for you, as well as a help article on installing a brake controller.

expert reply by: Victoria B

click to enlarge

Excellent 2.

5/26/2024

With the latest cars, it's a very good idea to place a diode in the RED wire to prevent voltage from the controller feeding back into the stoplight switch wiring harness. Feedback from the controller can cause all kinds of problems with cruise control, error codes, shifter locking up etc. I'm using the universal harness you suggest # 20127, but will place one diode (as noted above) in the RED wire and another diode in the BLUE wire to prevent trailer battery feedback from going back into the controller. Hope this helps someone avoid having problems after a brake controller install.