Brake wire

[Sixth Floor]

Hello I hope this question hasn't been asked as scrolled around and couldn't find anything on this but what I have is a 09 Chevy Silverado Ltz 1500 4wd with 5.3l and I am adding under glow rock lights and these work in junction with turn signals and brake lights i have the turn signal lights working with the rock lights but not 100% sure where i can connect the one wire i have for the rock lights to the brake light so the rock lights work with brake lights? I think the brake wire is light blue but not exactly sure where it is? I am sorry if this was confusing. Please any help would be very much appreciated. Thank you for your time.

[Jsdirt]

Either the green wire (right) or yellow wire (left) run the brake lights in the rear  - just tap into whichever one is closest.

 

Or light blue for the 3rd brake light (CHMSL).

 

EDIT - sounds like the signals have a separate circuit from the stop lamps on those aftermarket lights, so your only choice would be to tap into the 3rd brake light.

Edited February 4, 2025 by Jsdirt

[Sixth Floor]

Ok that won't be a problem but do you know where I could splice in by any chance? Preferably under the hood somewhere would be ideal but if not its no biggie?i have a wire ran to the back already but i cant find a light blue wire in the cluster under the bed in the back i do see a royal blue wire though. Ok i havent tried the yellow wire yet. The green one with rock lights on turn signal flashes yellow and red when right blinker is on so cant be the green i guess i will try the yellow and see what happens .

Edited February 5, 2025 by Sixth Floor

[Jsdirt]

I can't remember offhand, but there should be brake light power in either the under hood or interior fuse blocks.

[Sixth Floor]

And just to confirm that's going to be a light blue wire? Would running straight to the brake switch you think that would work?

[Jsdirt]

I don't know if it's blue up there. You would need to check and make sure power is downstream of the switch, otherwise you will have just a constant 12V there. If it isn't blue, it's probably a good bet that it is NOT switched there. I'm thinking I should tell you to disregard looking up there since that is probably the case. I just can't remember - been a long time since I've done electrical troubleshooting on a 900-series truck.

 

You might have to fish a wire down from the 3rd brake light down through the sheetmetal of the cab - that would be the best way of doing it. Having a snake of some sort would be mandatory, whether an actual wire snake, or something made out of metal coat hangers.

[Sixth Floor]

Ok but it will be light blue wire at the 3rd brake light? i can do that won't be a problem. Thank you for all your help Jsdirt!

 

[Jsdirt]

I can't tell you with 100% certainty, but I'm FAIRLY certain it will be blue there. Best thing to do is get a test light, then get a helper to hit the brakes while testing.

 

On that note, IF I remember right, on the 900 series trucks the brake switch was KEYED. In other words, the ignition would have to be ON (engine doesn't have to be running) in order for the brake lights to work, so don't let that take you down a rabbit hole. Most vehicles aren't wired that way - every other vehicle I've ever seen the brake switch went straight to battery power, whether the ignition was on, or not.

 

You're welcome, man! Hope everything goes smooth in hooking it up.

[Sixth Floor]

I will give you a update tomorrow and let you know how it turned out 

 

[Ianf]

If you do not have a factory trailer brake controller, there is a CMHSL wire taped up under the dash. I believe the wire is orange on these trucks and it should be marked.It is in the aftermarket trailer brake controller bundle. Look it up in gmupfitter.com.

 

It is up by the steering column.

 

 

[Jsdirt]

Ahh, yep - forgot about that. Tucked between the column and parking brake, taped up very heavily.

[Sixth Floor]

I did confirm orange wire with test light prior to install and that was the CMHSL. 

Edited February 6, 2025 by Sixth Floor

[Sixth Floor]

You're the man bro! Thank you so much. Install went perfect. Thank you again for your help! 

[Jsdirt]

NICE! Glad to hear that! 

 

Thanks for the follow-up.