Wiring a third brake light for a truck cap on a Chevrolet 97 K1500

Quick way to wire in a 3rd brake light for a cap without using a logic box that doesn't always work.
Again this is a quick way of doing it. I only did it this way due to the weather condition and will run a stand alone wire in the future so I can wire up the blue and orange wires for a brake controller.
Not shown in the video is that I ran one wire to the ground in the tail light to the 3rd brake light.
If your truck does not have the blue and orange wires in place from the factory, you will have to run a wire from the relay to the back of the truck. Follow the existing wiring and zip tie it to it.
** Please take note that the wires that I used are for using a brake controller and using the AUX terminals in the fuse relay center. **
I am using the white wire off of the Brake lamp relay output. This sends 12v when the brakes are applied. This allows for adding a third brake light without having the turn signals or marker lights interfering with it.

[@MrTaxiRob]

Just went through this with my Suburban when trying to rewire a trailer plug. There is a separate pigtail taped off inside the rear left side lighting harness that you can use for either purpose. The one 10ga wire within that pigtail is the 3rd brake light wire. C/K and Suburban Tahoe had generic wiring harnesses, if you have the tow package it will be there on any OBS truck. The ideal setup would be to use the pigtail for your camper top, and use a Curt or Hopkins T connector for the actual trailer harness if you are running both at the same time. That's about the cleanest way to go, and the location of that pigtail is set so that you can run it up inside the left rear corner of your bed.

[@AAA-cu8rk]

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[@bgd73]

I have never found an answer for those with no brake controler. ..with just a truck cap trying to abide by laws. my truck doesn't even have a blue orange wire. eidt: it didindeed have one..it was so old the end of the blue turned a strange ornage/ yellow..and the little white wires is the full 14 volts brake trigger.

[@StormLaker]

I think if you have trailer harness, you can tap into the wire there too

[@rosincore]

You can if you have the 7-way installed. If you pull off of the 4 way you can only have running lights or turn signals.

[@MrTaxiRob]

@@rosincore there should be a fifth wire (white) in the rear light harness coming from the left side, that is wired to the 3rd brake light circuit. I thought it was a loose ground but it blew my brake lamp fuse when I connected it to the frame and hit the pedal (fuse #1 in the dash box.)

[@leemp337]

98 chevy k1500. I have a 7 pin installed with a brake controller. They are attached to the fuse box under the hood already. Can I tap into the blue wire going to the 7pin for my 3rd brake light and the orange wire for camper dome lights?

[@MrTaxiRob]

There should be a fifth white wire either in the camper top pigtail located in the rear left side lighting harness (it will likely be taped off if it's never been used,) and there is also one in the center rear lighting harness (where you would normally install a 4 flat T connector) coming from the left side.

[@minivan4x466]

Hi. Did you just conected back brake wire to white wire before relay? So power to the back runs without relay? I need to conect main brake lights like this (without flashing) but I am afraid of too big load on white wire

[@rosincore]

It is after the relay. The white wire is voltage sent from the relay.