Issues with Leer 300200

Hey folks,

I'm new to TW, but I've searched around and haven't found a thread with my issue so I'm starting a new one. Buckle up, it's a long one

I got a Leer 100XR cap for my 2020 Tacoma. It didn't come with any wiring harness since I bought it off Craigslist.

So I bought a Leer 300200 wiring harness from EZWheeler which connects inline with your 7-way tow wiring plug to get the brake signal and ground.

EZWheeler annoyingly didn't include the 26' fused power line which you run to your battery for constant 12V for the dome light. But the YT video walkthrough they have for this product also doesn't show the fused line for the dome light, so I thought maybe it wasn't just me, and worst case at least my third brake light on the cap will work even if the dome light wont.

I wire everything up and press the brake, but no love on the third brake light on the cap!

I got the multimeter out and went to work and everything checked out, fuses are fine, continuity all the way, 7-way tow connector pins are still receiving voltage. So I got a 12V battery out and connected it to the 300200 harness where the missing 26' fused line to the battery should connect and voila my third brake light came to life!!

So now I'm left scratching my head, since the wiring diagram (see below) shows that the 12V for the dome light (black) and the third brake light (red/CHMSL) are separate power pins along with a common ground (white). I don't see why the dome light needs to have power for the third brake light to work.

Has anyone else installed one of these before? Anyone have ideas for what I'm doing wrong/missing here? I've been banging my head against this all evening.

Thanks in advance!

Leer Junction box:

Wiring Diagram:

Junction Box with my new harness connected:

 

when I had my lear and my current shell tapped into the break light for the 3rd. Is this box connected to any of the taillights? If not then likely wont work with the brakes. Pretty easy just need to get the light. there is guy if you search that makes a nice plug and play adapter that gives you all the wires you need for any rear light setup.

 

Nothing tapped into the break lights. The Leer #300200 connects inline with the 7-way tow harness to get the brake light signal from there, so that you don't have to tap/splice any wires in your tail lights. Which should be nice and convenient, if I wasn't having issues

 

Gotcha, I got nothing for ya then Sorry. I am sure someone here has used this thing. When I added the new setup I used the plug and play harness a member sells for this.

When I bought my previous Leer shell new they did not include this thing either.

 

One of these came with the Leer I just picked up. I was planning on running my own line from the battery so I could have a 12-volt socket in the bed for a cooler (ours uses 5 amps), but I noticed this has pin 6/aux with 10-amp capability, presumably for a cig lighter socket?

Mine is set up with just the dome light so pin 6 is unused - is there an official accessory that adds an outlet or would I be better off running my own line from the battery? That way I could put two outlets back there and use one for the cooler and the other for a USB/cell charger, etc.

 

I haven't seen any official output harness for that Aux out connector. I feel like they just had some extra pins on the 6-pin molex and thought :shrug: "let's call it 12v aux".
If you want it to look tidy you could just buy some 6-pin molex connectors online so that you can use the leer junction box/fuse. Run your own line from the battery into the bottom of the junction box and then run whatever you want from out from the junction box (e.g. a splitter with two cig plugs).