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Routing Aux wires through headliner


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I have done some searching, but did not come across any similar results to my discussion.

 

I have a 2015 Sierra 2500HD Denali with the snow plow prep package. My goal was to route a set of wires from the Aux switch in the upper console to the rear of the truck by the 3rd break light in order to hook up a roof-mounted light.

 

I started by removing the upper console switch "plate"; it is only held in by clips. I then removed the switch plate housing by removing the two screws with a T10 torque bit. the rest of the housing is held in by two clips. I also removed the 3rd brake light, naturally. I successfully pushed a piece of 12 awg SOLID wire, starting from the front of the truck, working my way back. I found that removing the rear dome light assembly aided significantly to help guide the wire from that location.

 

Once the wire reached the rear of the truck, I used another short piece of solid wire and shaped a hook on the end in order to fish the end of the longer wire through one of the top holes behind the brake light. The small hole is not ideal for permanent wire as the hole is a bit small.

 

I reused my shorter piece of wire and made a large bending radius to loop it from the large, bottom hole to the smaller, upper hole. This will allow me to fish the permanent wires from the small, upper hole down to the large, bottom hole behind the 3rd brake light. Note: I was not able to hook the wire through the hole that the long wire originally popped through, so I had to use the next hole to the right. (I later fished the long wire over one hole with my hook).

 

Next, I cut a length of 12 awg STRANDED wire and left PLENTY of extra just in case. I then tied on the wires to my short piece of "fish" wire to get them out the bottom hole. The small, upper holes are only large enough for two wires to pass through, so I had to stagger the wires as I fished them through. I then tied the other end of my permanent, stranded wire the long solid wire that runs the length of the truck roof. I was able to effortlessly pull the wires to the upper console in the front of the truck. 

 

From there, you can solder them to the flying leads left by GM above the upper console for the aux lights. My truck still had the aux switch disconnected from the assembly line, which is typical. Obviously, that will need to be connected in order to use the factory Aux switch that comes with the snow plow prep package. 

 

I did not make a hole in the 3rd brake light at this time to get the wires to the outside of the truck. I will do that at a later date when I get my roof-mounted strobe light. For now, I tucked all wires above the headliner and behind the 3rd brake light. 

 

I hope I was able to explain this process clearly enough to understand. I did this by myself, but a second person would have made this much easier! 

 

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Solid wire is never recommended for automotive uses. the vibration will break the wire and therefore leading to a short circuit and worse things.

 

The wire shown in the pictures that you are using can handle more than 20 amps at 12V. That is way overkill.

 

Hopefully you are using an LED roof lamp that will not require more than 4 amps. Therefore requiring a 16ga automotive wire.

 

There are methods to use for a safe and durable installation.

those include...

 

use existing wire installation through the body, this will minimize any problems with short circuits.

 

Low amperage wires to control the relay, 16ga wires as short as possible to attach to battery, for the relay you will need a ground which would be a great spot to grab ground for the light.

 

Make sure everything is fuse protected. 

 

Forgot, any wire that passes through a body metal hole has to be inserted through a isolating grommet.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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On 9/20/2022 at 6:26 PM, lovecars said:

Solid wire is never recommended for automotive uses. the vibration will break the wire and therefore leading to a short circuit and worse things.

 

The wire shown in the pictures that you are using can handle more than 20 amps at 12V. That is way overkill.

 

Hopefully you are using an LED roof lamp that will not require more than 4 amps. Therefore requiring a 16ga automotive wire.

 

There are methods to use for a safe and durable installation.

those include...

 

use existing wire installation through the body, this will minimize any problems with short circuits.

 

Low amperage wires to control the relay, 16ga wires as short as possible to attach to battery, for the relay you will need a ground which would be a great spot to grab ground for the light.

 

Make sure everything is fuse protected. 

 

Forgot, any wire that passes through a body metal hole has to be inserted through a isolating grommet.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I'm not sure if you read my write-up or just looked at the pictures but, I only used the solid wire for means to pull the stranded wire through the headliner. Also, your claim that I can only use 4 amps for the aux roof light is inaccurate. According to the owner's manual, the auxiliary roof beacon light circuit (that is factory installed with the snow plow prep package) is rated for 30 amps.  The 12 awg MTW STRANDED wire that I used is rated for 30 amps. I used MTW wire because 1) it is what I had laying around, and 2) it is more durable than "automotive" wire. I do agree with you that the hole that I used to penetrate the wires through needs to have some sort of grommet to protect the wire from the metal opening. 

 

Your further explanation of how to wire in a relay, while practical in theory, is not necessary in my installation as the snow plow prep package on my truck comes with a factory installed relay rated for 30 amps. 

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