Bed Cap Install & Wiring Issues

[47G2A]

Confirming that this solved my issue. Thank you greatly!!

Thanks for confirming that it worked out for you.

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[rockfish]

Nice! I am going to try it also. Of course that means that brake light could quit working if Ford does something to change that setting.

 

[DadBald]

Hi folks, I just wired up my cap brake light to the wire under the hood. I checked FORScan but it was already enabled so good to go.

The issue in having now is whenever the light is in the dim setting it flashes constantly. Full brightness brake works fine, but at night when the running lights are on it just flashes all the time. Has anyone else had this issue or know how to correct it?

 

[Kanuck]

If you have a 12 volt test light...test the wire and see if the power is steady. If power is steady, there is enough "LEAKAGE" in the cct to light up the LED. You will need to add a resistor to the light to stop it flashing.

 

[Kanuck]

Just re read your post. That light should not be on with clearance lighting...only when brakes applied. There should only be one wire feeding that light and maybe a ground.


What make of cap?

 

[DadBald]

Ok, update, @Kanuck I think you're right. I took it for a drive this morning before the sun was up again (I can see it flickering in my bed cam). Brake signal works as intended and the light responds appropriately there. I think it's flickering when there is supposed to be no signal at all. It flickers under normal driving with lights on, with lights off, and even after I park the truck with key off for another minute or so. It's a fast blink, like 2x per second.

It's a Leer cap with CHMSL, dome light, and electronic lock. I have the fuse box mounted on the rearmost drivers side "pillar.". (Don't worry I've cleaned up these wires since I took the pic - Leer install left a bit to be desired)

I attached the pin outs I could find for this box too, in case it helps anyone else.

 

[Sojourner]

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]

I have to ask
With key off
And you press brake pedal
Does the high mount brake light on the cap come on?
If leer wired it using the ford jumper under the hood, the brake light on cap only works if truck is on or running
Leers, tapping of unlock circuit under passenger rear door wiring is also.. strange..and depending on how it was tapped can present issues.

Some installers cheat and tap the drivers brake light at the trucks rear brake light assembly
This can cause issues and flickers
As well as occasional brake light out notice on dash.

Can you see flicker with naked eye, or only with camera?
Cameras pick up the pulse of the lens, but our eyes do not readily

 

[Kanuck]

I would recheck the wiring. Also make sure that when the truck is running, and in park, there is no power to any of the wires. Except , maybe auxiliary power. Then make sure there is only power to the brake light wire when the petal is pushed. Other than that, without being able to put my hands on the system, hard to say what is causing the problem.

 

[DadBald]

Ok, update. This is getting worse

ignition on OR off, brake pedal depressed - 12-14V
ignition on OR off, no brake pedal - I get a sine wave voltage between 0.5V and 4.5V with a period of about 1 minute. It slowly creeps up and back down between these voltages, consistently.

Originally this cap was installed by Leer. They put the dome light red wire into a wire in the taillight. I haven't traced the ground, but the ground is 0V to another ground. They ran both the electronic lock wires (together in their own shielding) AND the CHMSL wire all in some wire loom all the way up to the driver kick plate in the door sill. Previously the CHMSL would flash with my left turn signal, which is what I'm trying to rewire to fix.

I re-routed the CHMSL red/white wire to the capped wire in the engine bay, which also gave me ~13V before I hooked it up (regrettably did not check the voltage with no brake pedal, but it's a straight shot to the back where I'm measuring from today). If my understanding is correct, the CHMSL wire forms a circuit with the ground which should just be going to the frame, so this behavior would have been present prior to me wiring it to the harness in the back too.

Maybe there's an issue with my ground wire, but then nothing would work (lock works fine, dome light works as described with lights on). It's either an issue with the signal on my CHMSL wire from the truck, or an incompatibility between that signal and my LED brake light.

Anyone else observe this behavior? What do?

 

[DadBald]

Some pics

 

[Sojourner]

Sorry that I can't be of more help. I used the wire pair in the engine compartment and it works flawlessly. I have not yet had the courage to attempt the auto-lock wiring. Really easy it was on my Ranger, but the wire loom for the lock function on the F-150 is intimidating. Operating space is one problem, that there are two pairs of similarly color-coded wire sets in that loom in the driver's side kickplate is another. Maybe Leer picked the wrong one? Though that should have nothing to do with the CHMSL.

 

[DadBald]

Can you see flicker with naked eye, or only with camera?
Cameras pick up the pulse of the lens, but our eyes do not readily

Sorry, missed this question. I know what you're referring to and it's not that, at least not in its usual manifestation. It's a strobe about 2 pulses per second. Definitely visible to the naked eye. Actually my son pointed it out to me first "why is the brake light blinking?" Very distracting.

 

[ReverendQ]

Sorry that I can't be of more help. I used the wire pair in the engine compartment and it works flawlessly. I have not yet had the courage to attempt the auto-lock wiring. Really easy it was on my Ranger, but the wire loom for the lock function on the F-150 is intimidating. Operating space is one problem, that there are two pairs of similarly color-coded wire sets in that loom in the driver's side kickplate is another. Maybe Leer picked the wrong one? Though that should have nothing to do with the CHMSL.

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

 

[roadPilot]

Just had a new Leer 100XQ installed on my truck. While I always do most all of my own work, I'm glad they did the install and wiring at no extra charge ...

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