Bed Cap Install & Wiring Issues

[DadBald]

Hey James, what gauge is the under the hood wire? I plan to run mine back for a similar lighting issue. TIA

Not sure, but it's quite small. 18ga maybe? You can find the wire pretty easily where your air filter box bolts to the frame.

Sponsored

 

[DadBald]

Update on my CHMSL saga. Found the ground - it's got a self tapper into the bed behind the tail light - seems to be solid, not that. Tried a 6 Ohm 50W resistor - didn't help. It lowered the voltages by ~20%. Brake light was maybe 10.5V and the sine wave "light off" voltage was still there, just between like 0.3-3.5V. I disconnected my wiring from the CHMSL wire under the hood and measured right at the stock wire - this behavior was still present way up there. So it's not my wiring or the ground or the LED light. It's the signal from the truck.

I went in Forscan and disabled the CHMSL wire. To my surprise, the brake function was indeed disabled, but the sine-wave voltage seeking was still there! ~0.5 - 5V over the course of 30s-1min or so, over and over. Why is this wire carrying this signal?

Saw the wiring diagram earlier in this thread. I did recently replace my rear bumper harness so I could fully utilize my 12-pin smart trailer connector. I used Ford parts for all that though... but could there be an issue with my trailer brake control module?

I drove around for a while without the CHMSL until I could try these things, but today I wired it back up the way it was. Now it flashes with my left turn signal, but at least it lights up with my brakes. Ugh.

Here's a video of the behavior with the "light-off" signal.

Ground.

6 Ohm 50W resistor I tried.

 

[ReverendQ]

I have the same setup. IIRC, you have to pin the connector first by inserting the wires into the provided connector. And again, IIRC, I initially started to pin the connector backwards (the directions leave something to be desired, frankly. At least for me). So maybe check that the pins are in the correct location on the connector?

My set-up - same as yours - works without issue.

@powerboatr, @Kanuck , @DadBald, Anybody who has a good idea, How did you route the wire from under the air box to the back. In the video on page one he speaks to running it down the high voltage "orange harness" and following it. However, that cable goes down and along the frame alright, but this goes up above the frame rail along the gas tank which I can do using some fish tape but I was wondering if anybody had a better idea? Pictures and/or video welcome TIA

 

[Kanuck]

I would be running it along the frame attache to a wiring harness. Bring it out by the power outlet. I would also use an all weather or semi trailer wire because of it location.

 

[DadBald]

My wires installed by LEER are routed the way you described. A little while back I ran a coax wire for a rear-view mirror cam, and I ran it straight down the frame to the back wheel well, up and over my wheel well liners, and you can either fish it straight into the tail light opening from there, or drop it back down to the bumper level and fish it up the internal bed structure to where I showed my ground wire was installed. There's basically 2 openings behind the tail light with a wall between them. Either will work.

This vehicle is cavernous in every way - If you can run the wire down and out of the engine bay, I'm sure you'll find an easy route to the back.

 

[DadBald]

Here are a few pics... not sure how helpful they'll be. I ran it inside some wire loom and zip tied it up where I could, usually to another harness.

Since my camera feed goes into the cab, I tried to run the wires up and over the cab mounts in case for whatever reason it needs to be removed. Something to consider depending on where your wire goes from and to.

 

[powerboatr]

@powerboatr, @Kanuck , @DadBald, Anybody who has a good idea, How did you route the wire from under the air box to the back. In the video on page one he speaks to running it down the high voltage "orange harness" and following it. However, that cable goes down and along the frame alright, but this goes up above the frame rail along the gas tank which I can do using some fish tape but I was wondering if anybody had a better idea? Pictures and/or video welcome TIA

i ran mine in protective convoluted tubing through the frame
i have a long fish wire, stuck in in a few feet then out the next hole and did this a few times until wire was at the rear of truck
this way its really protected and no need to zip tie or fasten it except at ends
did my rear led light harness the same way

 

[DadBald]

Hey, question - where is the BCMC module physically located? Is this the fuse box under the hood? I'm wondering if my weird voltage issues are being caused by my pedestrian sounder override that I installed to switched power at an open fuse there...

Also, AI faux-pa of the day:

Thanks, Gemini. I'm 100% certain my main fuse panel is in fact not located in my tailgate step (if I have one)

 

[DadBald]

I went out and checked my fuse box. I checked about 15 fuses or so, and they were all a steady ~12.5V or 0V; didn't matter if my ped sounder override was connected or not.

I checked my 7-pin trailer connector, and with the truck off the Aux/12V pin was giving about 0.8V? Otherwise all others were 0V dead. None of these checks found anything resembling my 0.5-5V sine wave voltage of the CHMSL wire, which I confirmed was giving me the same behavior during all these other tests.

I'm stumped... but I'd love to find a solution. Does anybody know anything about the BCMC module or the CHMSL wire or the Brake Control Module that might give any clues as to why I'm getting such an odd baseline voltage fluctuation on this wire?

 

[RAYJAY]

Not sure if it helps with the topper wiring, but when I was trying to get brake and backup lights on a bike rack without triggering the trailer stuff (I wanted to keep BlueCruise active), I used a harness designed for flat towing the truck which plugs in between the taillights and their harnesses.. that made it so that I didn't have to tap into any factory wiring.

The harness I bought was a used return on amazon that turned out to have the connectors not pinned correctly, but with a little testing, it wasn't too hard to remove and repin the harness connectors correctly (and add the reverse light wire and a 5 pin flat connector to it).

Here is the harness I used (I payed less than half the current price for the 'defective' returned item):

https://www.amazon.com/dp/B0BRNZG9HL

how did you tap into the backup lights? epin one of the conectors?

 

[travisN000]

how did you tap into the backup lights? epin one of the conectors?

Its been awhile, I'd have to pop the tail light out and look

I had help from my brother who did complex vehicle electrical for a living for awhile, but IIRC he probably just tested for and tapped the existing wire in the adapter harness near the tail-light; I do recall replacing the 4 pin with a 5 pin for the backup lights, and wrapping it all in a plastic loom while he sorted out the correct pinout at the tail-light end

Sponsored