2019 Colorado GFC third brake light

I need help wiring my GFC’s third brake light. I have a Chevy Colorado.

I have this Brake light Logic module # AT-LC-8N
This is a picture of the module and wiring the instructions.

This is a picture of what I have behind my driver side taillight.

There are 4 wires from the trucks taillight wiring: black, grey, yellow, orange. I have the logic module mounted with double sided tape down out of the way. The crimps haven’t got the heat to weather seal them yet.

The logic module is wired as follows:
red/white wire to third light
black wire to third light (i think this might be wrong) should the black wire be grounded to the truck?
yellow wire to ?
green wire to ?

Thanks for the help.

Do you have a different 3rd brake light than every other GFC? That module is not needed with the GFC 3rd brake light. You can just install the posi taps to the light that brightens when you apply the brakes.

If you need a specific wiring diagram I can post that, just need to wait till I get to work and I have some free time. You can also try searching coloradofans.com or zr2zone.com and see if there is something there first; it’s not different from a 2015+. If you are trying to install that to get it to blink on right and left turn signals you are going to need to run a wire to both the right and left side. Also I would not be using those type of wire connectors in the rear, it will short out over time because they are not waterproof (ask me how I know). I would use these, they have solder on the inside and you just use a lighter and it shrinks onto both ends and joins them with solder, so it is a permanent connection without all the hassle of using a soldering iron.

No the camper’s third brake light is the standard light. My understanding is that the Colorado has a combined turn/brake light. Is that wrong? The module is there to stop the campers brake light from blinking when using turn signal. I read that here. I searched the forums you mentioned but didn’t find much. I will admit my internet search skills are lacking though. I will get some of those solder connectors thanks for the tip.

@Zkzr2. If the Posi-taps can go straight onto a brake light wire I would prefer to do that. That seems cleaner and easier to me. I think our trucks are similar. Which wire did you use the Posi-taps on for your install?

There are 4 wires that run into the taillight housing Yellow (i think is the backup light because it runs to the middle clear lens), black (i think is the ground), grey (i don’t know), and orange (i don’t know). The left driver side is the exact same, just mirrored, from right passenger side. Here’s a picture of the passengers side taillight housing wiring.

Full disclosure, mine blinks with my left turn signal. I’ll have to look at that module though, seems interesting. I don’t care that it blinks realistically. If I remember right I used the middle bulb yellow wire. I’d have to take it apart to see though. I think the third brake light is supposed to be off when your lights are on and only brighten when the brake is applied. Unfortunately I don’t believe there is a bulb in the rear that does that. Maybe the top one? I have to take mine apart soon anyways cause it has a burnt bulb. I can check this weekend though when I have my truck.

Well, I just ended up just nixing the logic module for now. The camper’s brake light has the same function as yours now, lights up when braking and blinking with the left signal. I found this if it helps anyone in the future.

To get this working (sorta) I used the left driver side rear taillight.
Camper light red (+) wire to truck taillight grey wire
Camper light black(-) wire to truck taillight black wire.

I added some LEDs to the camper today, lights in the truck bed and some in the sleeping area. Much easier than that :rage: brake light.

Yeah that sounds about right. BTW if you have the bed light accessory you can tap into that and add a button switch so you dont have to go into the cab to turn it on. I wired mine in tangent with the trailer so it always has 12V. Currently it’s not working cause it shorted out from those connectors. Once winter is subsided I plan on redoing the wiring with a more water proof solution. The button in the rear is such a nice convenience.

Got any pictures of the button setup?

I removed it all currently, so no, but I used this and plan on getting another. It fits perfectly in the upper round hole on the driver side by the tailgate. Just wired it to a trailer harness and used an extension to connect to the switch. You have to re-pin the trailer T harness so 12V goes to the 4 pin connector otherwise you don’t have 12V supply. I have the bed light package, so I just exposed some wire and soldered to it. I’ll probably just use posi tap as it’s connected in the bed and that part is mostly protected from the elements with the GFC. Below is my diagram for this switch and what my plans will be. I only connected current lights without a blue sea panel initially but will do the full thing this spring.

I’m late to this thread, but I located what seems like a pretty easy fix. After trying a different brake logic module and a fuse add-a-circuit, both unsuccessfully, I located the wire leading to the CHML in the cab and spliced into it there. Its under the kick panel trim on the left side doors. Pics are of the left rear door on a crew cab. The wire is purple with a grey line on it. It was right on top of the bundle of wires in my truck. Tested it by sticking a sharp test light probe through the plastic and found it on the first try. Ran the new lead through a plug in the floor under the seat and then along the frame to the camper wires.


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Is that just the positive terminal? Where does the other lead from the camper go?

It would be a + or power lead. The other wire should be ground.

This sounds like a decent solution if you don’t want your third brake light on your camper to blink. If you don’t do this, you do need some type of “logic” controller. This is the one I use on my canopy.


Each yellow wire goes to the brake/signal wire on the left and right. The green wire goes to the +/power of the brake light and the ground wire for the third brake light is grounded to my truck body. I just ran a wire from the right side to the left and tucked it all behind the left taillight.

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Sorry, late again! Yes that’s the positive lead. I grounded mine behind the left taillight using the tailgate catch post. I ran the wires through the bed via an abandoned riv-nut hole formerly used by my Leitner rack.