WTF Wiring for Cap 3rd Tail Light.

Replaced my cap with a wedge camper. I'm trying to hook up the 3rd tail light using the wiring the installer did when the cap was installed. Who is the Chucklehead? Him or me?

He used a 3 prong SAE connector and didn't seem to follow the color code for trailer wiring. He extended the 3 wires by using 2 black wires and a brown wire. The brown wire is tapped into the green-brown wire on the harness which I'm guessing is the brake light. A black wire is tapped into the white-black wire parking light and looks to be the constant. Correct?

The second black wire (not seen in the pic) is run all the way up to the positive post on the battery. in addition, there is a 5a inline fuse at the tail light and a 15a fuse at the battery.

I thought I would find one ground, one constant to a running light, and one to the brake light. What's up with the 2 fuses? Why run all the way to the battery?

I'm confused.



I hate those add-a-taps but they have been there for 7+ years and I'm thinking maybe if it ain't broke, don't fix it.

I do have the stock trailer harness and have no ideal where the cab's 3rd brake light connects.

Oh, I'm swapping out the 3 pin SAE for a generic 3 pin auto connector from Amazon.

 

Many toppers want brake, ground and dome. Dome can be constant from the battery and manually switched. Or it could come from a cargo circuit (readily available for 2020+ Tacoma in the taillight.

A fuse is required when pulling directly from the battery. It’s a little redundant for the brake circuit but does ensure that if the third brake shorts, you don’t lose primary taillight brake signal.

 

Also, white w black stripe is ground for Toyotas. And accessing the cab 3rd brake light is a little harder than grabbing it from the taillight so rarely done because it’s all the same circuit.

 

Dome light, didn't think of that. So I can cap that wire. I only need 2 wires for the 3rd brake light. So I'm the Chucklehead... well the installer still put 2 fuses inline with the positive he ran from the battery.

Thanks for the help.

ETA:
Wait! I'm still not right. The "new" 3rd brake light has a ground, a brake light, and a running light. So I want to connect to the green wire on the brake socket for the running light correct?

 

I’m unsure of wire colors downstream of the intercept as I’d have to look at my set to know. The 6 position intercept (5 wires, one plug) is where my T harness goes, not at the bulb adapter. At that intercept, blue is brake and green is parking lights. It’s typically outside of the taillight cavity near / under the rear bumper.

 

Thanks!

 

Bought the FBC harness and installed it. Quality piece, nicely labeled. It's the right way to do the job.

Can't say as much for the wedge camper wiring. Looks really nice, heavy duty shrink tube. In fact, it is nice. Except. For another reason I had to remove the back door of the camper. I had to cut through shrink tube to disconnect the wiring. This revealed they used bullet connectors. Heavy duty bullet connectors. With much difficulty I parted the connections, got the door off, got the door back on and was in the process of pushing the connectors back together when I decided it was a good enough connection to test the light. It didn't work.... I had power to the bullet connectors so I stripped the shrink tube back another inch or so to reveal with the heavy duty bullet connectors the weak point became the 20-22ga wire used for the LED tail light. 2 of the 3 wires had broken at the squeeze point of the bullet connector.

So I bought a 3 wire waterproof connector off Amazon and will use that instead of horrid bullet connectors. Hopefully the 3 short wires, that are now shorter, out of the tail light are long enough to properly solder to the new connector, or I may need to get another tail light off Amazon, which do match the origional, but only sold in pairs.

Seems like it's never easy.

 

I have done some 3 way disconnects for people in the past. And I have longer options too. But if you’re all set then cool. I like it when people DIY and I think the non OEM harnesses are the perfect spot to tinker.