How to Add a Center Mounted Third Brake Light to a Trailer

Updated 06/15/2020 | Published 06/13/2012

Question:

I have a 2002 Nissan Xterra with a 4 wire flat connector. I want to add a third stop light to my trailer. This light has a second bulb for a running light and license plate light. The only success so far still makes the third stop flash when turn signals are applied. If I add a six wire converter to the truck how do I make the third light connect to brake? Thanks for any suggestions.

asked by: Kevin G

Expert Reply:

Although it is not required by law, what you are wanting to do is certainly possible.

Because trailer tail light systems combine the stop lamp and turn signals for each side onto a single circuit, you will need to use a vehicle-to-vehicle tail light converter, part # 118158 to split the brake light circuit back out.

The white wire on the input side of the converter would ground to the trailer frame, the green input wire would tap into the right turn circuit on the trailer and the yellow input wire would tap into the left turn circuit. The output side of the converter also has three wires. The yellow and green wires are not needed for this application, and could be cut short and should be capped off. The red wire would connect to your third stoplight, with the light also grounded to metal on the trailer frame.

Looking at the diagram I produced for you will give you a good idea of the wiring layout.

expert reply by: Mike L

click to enlarge

Eldon

6/9/2020

How do you wire a third brake light for your shell, without using a lead from your 7 pin trailer hookup? If I use the lead from my 7 pin trailer hookup, my controller in the truck cab always has the green connection light on, like it is connected to a trailer. Thank you

Chris R.

6/12/2020

You can simply wire the 3rd brake light to the factory brake light circuit behind the tail lights (instead of to the trailer wiring harness). If the turn/brake light circuits are combined on your truck, you can use the Pacer Module # PP20-702 to filter out the turn signal so the brake light doesn't blink while you're turning.

Eldon

6/12/2020

@ChrisR Thank you