Cargo Lights as Back Up Lights

micl9

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EDIT - If you have a Lariat this will also turn on your puddle lamps! This is the stock functionality, when you turn on the cargo lights the puddle lights also come on. I just finished adding Lariat mirrors to my XLT (XLariaT) and wired them this way.
see POST

My old Frontier had this function from the factory. When you put the truck in reverse the cargo lights would also come on. Once I upgraded to brighter LEDs for the cargo lights it was a great feature with a back up camera.
If you want to keep a stock look and easily add more backup light keep reading.

I spent a bunch of time mapping this out and confirming functionality. Used the wiring diagrams and a multi-meter to be sure. Now I just finished making the mod and it works great.
The Cargo dash switch is a momentary switch that sends a gnd signal to the BCM telling it to turn on the Cargo Lights. Another press will shut them off. The BCM will also turn them off after the truck is locked or you go above a few MPH, in forward or reverse.
So all that is needed is one relay triggered off the reverse line and wired for a momentary negative output. This is done using a cap and a resistor as show. The12VOLT.com is a great source of all thing 12V related and a ton of relay setups. I am not affiliated with the site, but a long time user. One other thing to note is the diode across the coil. I am not 100% clear on what it does, but they recommend it to keep voltage spikes from going back into the harness when the relay is de-energized. ie it protects your truck electronics. This can be added externally to the relay or you can buy a relay with the diode built in. THIS is the one I used.
constgtomg_ptn.gif

I plan to NOT use a common ground just to be careful - as I don't want the possibility of the reverse 12V getting to the BCN signal input.
Below is the wiring diagram I have put together and represents how I wired my truck. Wires shown as solid are stock wiring, those shown as dashed are the wires I added. Tapping in at the BCM (right below the cargo lt sw) will keep all the wires short and localized.
Speaking of taps I used Posi-Taps over T-tap crimp style as the later can damage the harness and the Posi-Taps are easily removed leaving only a small hole in the harness wire insulation.

I used THESE LEDs to brighten up the Cargo Lights. These are the same as I had in my Frontier and they lasted at least 5 yrs before I sold it.

Total cost was probably $20-30, including the LEDs (and the Posi-Taps are not cheap!!!). Full parts List with links below

FOLLOW THIS AT YOUR OWN RISK. But it did work for me, Install pictures to follow.
1608319010909.png


Parts List
  1. Relay
  2. Relay Connector (optional)
  3. Capacitor
  4. Resistor
  5. POSI-TAPs
  6. Brighter LED lights
Install guide in next post
Video further down HERE
Cap and resistor wiring HERE
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micl9

micl9

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Ok here are the step by step directions
Directions on the cap/resistor wire assy HERE.

Pop open the Interior Fuse Cover/ Steering Column Trim Panel
1608323047605.png


Remove the headlamp switch trim panel to give aces to the cargo lamp switch connector
EDIT - I could not get this to fully release, its has a screw above the cargo light switch. To remove that you need to also remove the vent/trim above. I was able to get to the connetor out without fully releasing the trim piece. Just be aware that the headlamp switch trim panel does not come out as the manual states! To elaborate on this - In the below graphic there is actually a tab in the upper middle of the switch trim(around the arrow) that is held in with a screw. SO POP OUT JUST THE BOTTOM and reach in and disconnect the connector. EDIT: HEADSUP!!! There is a screw not shown in the manual - see picture below manual image.. You will need to pop off the vent trim piece also.
1608326658422.png

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And unplug the connector from the Cargo lamp switch
1608330749088.png


Tap into to the 2 wires Black-Grey and Violet-Grey White! EDIT 4/4/21 thanks @port43 !
1608330898093.png


Tap into the Green-Brown reverse wiring coming out of the BCM
1608330827886.png


Relay attached - ground not yet
1608328301979.png


Install Complete
1608328464082.png

And the results
1608331071061.png
 
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cfhgarza

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Very nice. Get some action shots when you get a chance
 
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micl9

micl9

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port43

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Just to be sure......
When you turn your cargo light on, it does not activate your reverse lights, correct?
 
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micl9

micl9

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Just to be sure......
When you turn your cargo light on, it does not activate your reverse lights, correct?
No
Other way around plus some - when I put the truck in reverse the reverse lights activate the signal to the BCM, which then turns on the cargo lights.
 

viperwolf

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I really like how you used the BCM to control this. I would of went the other route bc I dont trust myself playing with the BCM. I would of just simply used a fused reverse signal with the relay to power up the cargo light when switched. I run a fused power source from my battery for anything I add anyway. Anything you do pretty much though, is playing with the BCM in some way. I like you took the time to figure this out and you used a diode/capacitor(in the diagram) with the relay. This also helps for low voltage chatter if anyone runs into that. Good Job and love the pics and information!!!!!!



One other thing, what is the 10K on the relay for?
 
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micl9

micl9

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Ok as Promised
Here is a video!
LINK
Notice that the reverse trigger is +12V, so when the reverse lights go out there isnt a second trigger and the Cargo lights stay on. The BCM then turns the lights off after fwd distance or speed is reached.

LOL and notice my son is worried he is going to run me over!
 
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micl9

micl9

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One other thing, what is the 10K on the relay for?
It bleeds off the voltage stored in the capacitor after the relay shuts off. I got all that from the12Volt.com, they are a great source for 12V relay schemes.

I was going to drive 12V off the reverse, but seeing as how the BCM applied voltage tapping a +12V line into that would also put 12V back to the BCM. It seems that its protected, but better safe than sorry.
And besides I don't get to Engineer much any more!😜
 
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viperwolf

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It bleeds off the voltaged stored in the capacitor after the relay shuts off. I got all that from the12Volt.com, they are a great source for 12V relay schemes.

I was going to drive 12V off the reverse, but seeing as how the BCM applied voltage tapping a +12V line into that would also put 12V back to the BCM. It seems that its protected, but better safe than sorry.
And besides I don't get to Engineer much any more!😜
yeah my cheap way, you would not have the cool delay effect of it switching off when you get to speed. I like small things like that. I mean you can put a really large capacitor(without the bleeder) to have a dimming effect on lights when they turn off, but its not the same.
I like things to have that factory style, I feel i accomplished something when someone cannot figure out what I did to make it different.
 
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P. A. Schilke

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It bleeds off the voltaged stored in the capacitor after the relay shuts off. I got all that from the12Volt.com, they are a great source for 12V relay schemes.

I was going to drive 12V off the reverse, but seeing as how the BCM applied voltage tapping a +12V line into that would also put 12V back to the BCM. It seems that its protected, but better safe than sorry.
And besides I don't get to Engineer much any more!😜
Hi Mike,

Faced with a decision in College to which way...Electrical or Mechanical Engineer, I chose Mechanical as I could not see electrons racing through wires at near the speed of light. I could not touch electrons unless I made a grievous error and shocked the hell out of me... Always wondered if I would have been okay as an electrical engineer...probably not...sigh....Great job!

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired
 
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micl9

micl9

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Hey Phil
LOL - I was deciding between Civil and Mechanical, hated chemistry so I went Mechanical, 1 less class! I mainly do house and auto wiring, I leave the circuit boards to the EEs.
 
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micl9

micl9

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LARIAT OWNERS HEADS UP!!
In researching my next mod, Lariat heated mirrors. I discovered that on Lariats the puddle lamps will also turn on when the Cargo lights are turned on. So, in reverse with my changes thr puddle lights will come on. This could be addressed by using a relay to switch 12V IGN to the cargo light feed wire instead of wiring thru the cargo light switch and BCM.
Or you could just learn to live with the puddle lamps being on when in reverse (you can see what this looks like by turning on your cargo lamp while in reverse). 🤷‍♂️

FYI - I am in the process of adding Lariat HEATED mirrors to my truck and will actual wire the puddles to the cargo lights. I figure the more light the better when backing up!
 
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port43

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Hello @micl9
I am guessing this is the capacitor and resistor, correct?

1611342983820.png


Did you have to make that or is it something that can be purchased?
 
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