Leer Shell Third Brake and Dome Light

Alright, hopefully I can find some helpful advice here I'm not getting much info elsewhere.
Bought a used Leer cap (Leer EA on the serial tag inside) a little while ago for my 2005 DC color matched and all. Has the third brake light and dome light wired (sort of). However, they do not have a quick disconnect 2 or 4 pin connector end. This is what the wires look like. They only have three female slide connectors. One was missing when I bought it.



Two sets of red and black wires, one for the dome, one for the brake light. I was going to run them directly to splice to my brake lights, but there is not enough wire left. And I'd like a quick disconnect set up for taking the topper off. From the looks of it, the previous owner just did this his own way, as everything I see online the cap already has the 4-pin connector wired and all I would need is a wiring harness like this to tap into the truck lights, and be done.

https://www.siraweb.com/wire-c90-907

Admittedly, electrical and wiring is far from my strong suit, so I need some help as to what I need to buy to make this setup work, and how to wire it. Do I need to just start from scratch and rip out the wiring already there? I reached out to my local LEER dealer and they wouldn't help me, and I'm sure I'd pay them too much for something I could probably tackle on my own anyway.

I'm probably going to just toss the wired dome light in there and get a battery powered LED one instead, removes the need to run a dedicated wire all the way to the battery, and also the risk of draining the battery if left on accidentally. So the big concern is the third brake light right now as my state requires it.

Any help?

 

Do you have a Harbor Freight around?
Buy this... Connect the 2 black wires together. Cut the new adapter (link above or one similar) in half. Connect the black wires to the white wire. Then connect the other wires to any of the other color wire on the connector and do the exact same colors to the otherside. Now you have a quick disconnect plug.

If you have a trailer plug connector, pin#4 is live when ignition is on. You can connect light to that for power.

 

I actually was at Walmart today and saw one of those, it was only about a foot long though. I did wonder if that would work if I cut it in half, but my concern was splicing different gauge wires together. I can't tell the gauge wire that are on the cap, they are pretty thin, maybe 18-20ga? Would splicing them to a 14 or 16ga connector cause issues?

And I do have the 7 pin trailer connector (tow package). So if I wire my dome light wire to pin 4, that's all I'll need for it to work with ignition on?

 

You would be okay splicing those wires together.

 

I had mine spliced into the driver's brake light wires.

 

Thanks, I'll give it a try and see how it works out and update here with pics in case that would be helpful.

 

Alright so an update. Went over to Harbor Freight and picked up the 25 ft trailer wiring harness as @Jim LE 1301 recommended. Watched some new youtube videos, and have a few questions.

1. Apparently on most new Fords, they left an unused third brake light wire hanging out under the truck in the wire loom that extends out of the cab specifically for adding a cap and wiring to the brake light. I searched front to back on the Tundra and couldn't find one. Anyone know if that exists on the Tundra?

2. I pulled the rear panel behind the back seat to try and trace and figure out the wiring for the rear cargo lamp and third brake light as option #1. I was thinking of taping into the cargo lamp for the rear dome light, so it turns on when doors open, and turns off when closed. Also to tap into the third brake light wire directly while in there. Also removed some of the panel from the passenger side wall to look in at the wires and there are a ton in there heading up towards the cab light. Anyone have an idea which ones I need? There is a black/orange, green, green/white, blue, white/black, black/white, and light green.


3. If option 1 doesn't pan out which I think is the case, I pulled the driver passenger light to take a look. There are 3 wires going into the tail-light/Brake light bulb. Black/white, green, and green white. Black/white is the ground I know, but which is the brake light and which is the tailight wire? Green or green/white? Don't have a volt meter, otherwise I would just check that way.



While I was out there, I did the wiper cowl leak fix with some RTV sealant (old gaskets were basically dust), and also did the rear window half-up actuator bypass. So not a wasted time at all.

 

Why not tap into the trailer plug for brake lights also?

 

Yea actually hadn’t thought about that. Would it be position 5 based on the diagram you sent?

 

5 or 6 but you may get a blink when using signals.
Not sure about the blinking.

 

Yea thats my concern, about the flashing third brake light when using the left hand turn signal. I checked on mine, and there are three rear bulbs. 1 reverse, 1 turn signal, and 1 tail/brake. The tail/brake being the one with two wires pictured above (one for brake, and one for tailight). So if I were to tap into the correct wire, I should only get it to illuminate when braking...but I could be wrong.

 

Looking through TW it looks like I can't tap into the 7-pin for the brake lights because it will blink when I use the turn signals. No go there.

Can't seem to find any information to tell me which wire on my brake/tail light bulb is the brake light wire. I don't want to tap the wrong wire. Also nothing is saying that I won't have the same blinking issue if I tap into the tail light.

 

Remove the bulb from the fixture, and and use a multi-meter to test the contacts in the socket.