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Topper Third Brake Light - Power Source?

Super T

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Going to pick up a Smartcap EVOa when my truck is ready, and I noticed their instructions indicate they provide a dedicated wiring harness to run all the way up to the brake pedal switch in the cab - that seems absurd to me, the light is literally as far as you can get on the truck from that switch. I've seen reference to a wire RAM provides taped up in a loom above the spare tire that's meant to be used for this purpose - when I asked my local Smartcap dealer/installer, he said yeah, they try to use it, but some trucks throw errors so then they have to use the harness off of the brake switch. What is everyone's experience with this? For a lot of reasons I would much, much rather just use the wire at the back of the truck if possible.

Thanks!
 
I successfully connected to the wire above the spare, it is all bundled up and tight to get to with the wheel in but possible.
If I recall there were supposed to be two, the red for the brake light and I think purple for a 12v but I never saw the purple.

No issues in over 3 years
 
I successfully connected to the wire above the spare, it is all bundled up and tight to get to with the wheel in but possible.
If I recall there were supposed to be two, the red for the brake light and I think purple for a 12v but I never saw the purple.

No issues in over 3 years
I only saw reference to the purple... first I'm seeing reference to two. If someone has a diagram from a service manual or other formal source, that would be pretty boss. Thanks!
 
No issues, I believe that’s what it exists to be used for. It’s where @Trooper mentioned, as pictured, above the spare.
Cool. Topper shop mentioned a red wire.... I wonder if they've been grabbing the wrong one and that's why they have trouble sometimes. Thanks again!

Begs another question, wtf are the other two wires for (assuming other sources are correct in saying there are three total)???
 
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Cool. Topper shop mentioned a red wire.... I wonder if they've been grabbing the wrong one and that's why they have trouble sometimes. Thanks again!

Begs another question, wtf are the other two wires for (assuming other sources are correct in saying there are three total)???
The factory could have changed colors? It should be easy to test the wire. I don’t know what the other wires are for.
 
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