Wiring Bed Cap

[braiden_patrick]

I have looked a lot into wiring my bed cap CHMSL and I can't figure it out. When I bought my pickup (used) there was already a connector in the bed that was in place from the previous owner for what I assume was a bed cap. It had a positive wire that ran to the battery with an inline fuse, a ground wire connected to the body of the truck, two wires that I believe I traced back to the lock/unlock of my tailgate (probably for an electronic-locking bed cap), and finally, a wire that ran to the factory CHMSL "white w/ violet" wire underneath my truck. Unfortunately, I couldn't find the other side of the connector that the previous owner had used, so I cut the connector off in plan of using my own connector (wire by wire to avoid shorting anything if I remember correct). I started the process of wiring my LED CHMSL on my bed cap, starting by twisting my negative wire to the factory CHMSL, and my positive to the positive that runs to the battery from the previous connector, but it didn't work. so then I did some troubleshooting. Does it light up when my lights are on? no. Does it brighten when I brake? no. In fact, quite the opposite. When my truck is off and the light is connected, the LEDs light up at the lowest lumen output, and when I press on the brakes, the light turns off. I can't figure out what I am doing wrong, and as an electrician, I feel ashamed haha. Anyone have any ideas of what my problem could be?

 

[crash68]

I started the process of wiring my LED CHMSL on my bed cap, starting by twisting my negative wire to the factory CHMSL, and my positive to the positive that runs to the battery from the previous connector,

The third brake light should be wired to the ground and the violet/white wire. It only powers up when the brakes are applied.
Is there just the two wires going to the topper's brake light?

 

[braiden_patrick]

I know, when it is wired and I put the brakes on, the light turns off, and when I release the brakes, the light turns on but dim again. I have the correct wire, there is only a negative and a positive wire for my brake light

 

[jawzs2]

Look at about :50 - :55 seconds in on this video. I' sure there's better ones out there, but first one Dr. Google brought up. ram already has a wire dedicated for that.

Third Brake Light Wiring Leer Ram 1500

How-to video on wiring in a third brake light on a 4th gen Dodge Ram, performed on a LEER cap but most likely works for other brands as wellAftermarket Light...

www.youtube.com

 

[braiden_patrick]

again, that’s the wire I’m using.

 

[jawzs2]

I started the process of wiring my LED CHMSL on my bed cap, starting by twisting my negative wire to the factory CHMSL, and my positive to the positive that runs to the battery from the previous connector, but it didn't work.

The positive goes to the wire from the harness, ground can be anything

 

[braiden_patrick]

I’ll give that a shot, we’ll see how it turns out

 

[braiden_patrick]

so where does my negative wire on my LED go to if the CHMSL wire underneath the truck is my positive?

 

[Daw14]

Swap the pos and neg connection, a led only works one way

 

[crash68]

so where does my negative wire on my LED go to if the CHMSL wire underneath the truck is my positive?

ground it to the frame

 

[braiden_patrick]

Got it to work, positive is the CHMSL wire underneath the truck bed, negative wire comes from the battery!