Wiring up 3rd brake light on Astro shell?

[Larry Hampton]

I just bought a used Astro shell for my 2003 truck and need to wire up the 3rd brake light.



I read another post about finding some wiring marked CHMSL or something like that but I didn't get a clear idea of it's location. The PO said he wired it into the left tail light but my Ford Tech buddy said if I do that, the light will blink when I turn on the left turn signal. He said to look for a wire or wires that look capped from the factory under the truck. I found a pair of small such wires near my trailer light wiring harness, one appeared black and one appeared black with a red stripe. Since they're short and I have a hidden hitch installed and big hands, I'll have to drop the spare to get a better look, are these the wires I want to use?



I intend to tap into wiring for the the 12v plug in the bed for the interior light and run it up to the sloped part that the rubber strip that 'seals' the tailgate attaches to and thru a hole with a rubber grommet. I'll run the 3rd brake light wiring thru here as well.



It would be nice to put the topper wires into a plug and have a flush mount to plug into, maybe I can find some trailer wiring kit.

 

[TRACket Paul]

The CHMSL wiring will be near the bumper between the trailer connector and the Left tail light.

Light Green is the positive connection (brake activated) on the CHMSL line.

Black is the ground on the CHMSL.

 

[Todd Z]

I found mine directly between the spare tire and the rear bumper...



Todd Z

 

[Mrlunchbox]

Good topic! I am in the same boat, I have a 2003 ST with a used cap I recently purchased. The cap has a dome light and a third brake light. It has some wiring and a plug. From what I gather if I look under my truck for this CHMSL plug/wire I can tap into that for all my "cap" needs? :banana:

 

[Brian Barham]

I am glad I found this forum. In the past few days I have had a lot of my questions answered by others posting before I could. Like said above I myself just bought a used cap and was wondering where that wire was. Mine also has a dome light. At first I thought it was battery powered, but I guess that answers my question on why there were so many wires to the harness. The guy I got it from offered little detail to the cap. He was so helpful I only got 3 clamps. At least it was less than half the price of a new one.

 

[Mrlunchbox]

I second that Brian, this site has been so incredible for me. I am very glad it exists.

 

[Larry Hampton]

Well, on my 2003, they're black and black with a red stripe. I just went out with a multimeter and cut the tips off and had a co-worker hit the brakes and those are it.



I'm going to route wires in a plastic sheath up to the area behind the tail light. I'm going to pick up two more wires off the wires that go to the 12v plug and I'm going to wire them to a flat 4 trailer plug. I'll wire the 4 wires from the shell to the other plg and I'll be able to plug and unplug the shell in the event I need to take it off.



This is unless anyone has a better solution.



Larry

 

[Mrlunchbox]

Larry, I was thinking of doing the exact same thing. If you get any pictures of the task or make a project out of it that would be great! That way we could all have something to go by. I will attempt to do the same when the time comes. :banana:

 

[Larry Hampton]

I plan on doing a write up on it.

 

[Mrlunchbox]

Awesome!

 

[Larry Hampton]

Got 'er done last night, getting ready to write it up, where do I put it? Here and they suck it out?

 

[Mrlunchbox]

I haven't a clue... maybe ask Todd? Start a new thread asking him so he will see it.

 

[TRACket Paul]

FYI:

 

[Larry Hampton]

Thanks Paul, I just submitted it. :banana:



Larry