12volt power in back

[elk_hunter]

Hi guys,

 

Does anyone know if there is a place to tap into the back of the truck for constant 12v power, for a light switch in my topper? If not ,where is a close place to get this?

 

Thanks

 

 

99 Gmc Sierra ext cab

[mdub]

Assuming you have a hitch, the trailer wiring plug has +12Vdc available. You can even buy an adapter for the hitch plug that provides +12Vdc via a cigarette lighter type plug. In your case, you most likely want to just want tap into the appropriate wire of the hitch wiring. A voltmeter will tell you which is hot. You may have to install a fuse in the fuse box to get the constant +12Vdc power (forgot which fuse... anybody recall?).

[mcreyaufmiller]

Do you have the 7 pin harness?

[elk_hunter]

No I do not have the 7 pin harness. I have the 4 pin one, and tapped that into the wires about the spare tire. but i think there are more wires down there that i didnt' use, didn't need the 7 pin, so why spend the $30 for it, when the 4 was fine.

 

i'll look tomorrow again to see what's down there.

[mcreyaufmiller]

No I do not have the 7 pin harness.  I have the 4 pin one, and tapped that into the wires about the spare tire.  but i think there are more wires down there that i didnt' use,  didn't need the 7 pin, so why spend the $30 for it, when the 4 was fine.

 

i'll look tomorrow again to see what's down there.

 

<{POST_SNAPBACK}>

 

 

If you had the factory 7 pin, there is a hot wire that comes to it to supply the battery and trailer with juice. If I am correct and you will have to check, I believe the newer trucks are pre-wired and have the harness already there. Other than that, you are better off using the converters rather than tapping into existing wires. the converters have safetys in them to keep a backfeed from blowing your computer.

 

Mike

[elk_hunter]

the trailer wires are back under my tire. I just tapped into get the 4 wires i needed and left the other(was over 2 yrs ago). So does all sierra come pre-wired for trailers? or only certain ones? And if all come with it, does that mean I have the constant wire you are all talking about?

 

I'll let you all know tomorrow after i crawl under and look.

[mcreyaufmiller]

the trailer wires are back under my tire.  I just tapped into get the 4 wires i needed and left the other(was over 2 yrs ago).  So does all sierra come pre-wired for trailers?  or only certain ones?    And if all come with it, does that mean I have the constant wire you are all talking about?

 

I'll let you all know tomorrow after i crawl under and look.

 

<{POST_SNAPBACK}>

 

 

 

My 98 does not have it, but do a web search for Reece hitches, or something like that and there should be ample information there.

 

I will make a call to my trailer guy and ask him, but he is not open until Monday.

[ManyCamaroz]

The '92 Yukon that I had and my current '99 had the wiring harness taped to the left side frame rail. The power wires were in a seperate bundle from the standard tail light harness. If you don't have this simply tap into the aux. 12v pole provided at your convenience center and run your auto/marine wire along the frame rail to where you want it.

[kdm101]

The 12V constant power feed is not live by default from the factory. My truck has the trailer wiring, but the fuse wasn't installed (just left in the glove box along with the brake controller harness).

 

The fuse is one of the big maxi fuses, 40A, and goes in the forward-most socket on the underhood electrical center.

 

On my truck, there's also a capped light blue wire behind the bumper attached to my 7-pin connector. I know this was a provision for a camper/cap, but I don't recall whether it's a switched 12V source (cargo lamp) or the high-mount brake light. A volt meter should tell you either way. The electrical diagram in my haynes manual is a big vague as it shows the CHMSL/Cargo lamp as one icon and 3 light blue leads to it.

 

And, as a last resort, it's quite easy to run some new wires from up front along the frame rail to the back to give the lights the power you want. I've done this twice now, once for aux lighting and a real heavy guage wire for my stereo amps.

[elk_hunter]

Well got under and looked. and besides the 4 wires for the 4-pin i installed, i also have 2 other wires, one that is blue and one that is another green. So i'm thinking I have the wiring for the constant 12 you have talked about, but just need to install the fuse, looking at the fuse in the hood, is this the 40a that is in pod #1 as it says on the diagram. next to is is 60ABS, then an AC, then ig,,,

[kdm101]

You got the right fuse, but I just looked at my 7-pin wiring. The hot lead is red. I also looked to see that the wiring loom itself runs directly up to the front, so it's not part of the rear lighting buss center.

 

Looks like you'll have to run some wires up along the frame.

[elk_hunter]

um..

 

wonder what the blue and green wire goes to, in the same loop with the trailer stuff.....i might drop the tire and see if that red wire is up there somwhere and i just missed it...

 

 

thanks for the info and all the help guys!

[99-2door]

the trailer wires are back under my tire.  I just tapped into get the 4 wires i needed and left the other(was over 2 yrs ago).  So does all sierra come pre-wired for trailers?  or only certain ones?    And if all come with it, does that mean I have the constant wire you are all talking about?

 

I'll let you all know tomorrow after i crawl under and look.

 

<{POST_SNAPBACK}>

 

 

 

My 98 does not have it, but do a web search for Reece hitches, or something like that and there should be ample information there.

 

I will make a call to my trailer guy and ask him, but he is not open until Monday.

 

<{POST_SNAPBACK}>

 

 

 

 

Your 98 does have it, they all do. It is a orange wire that is pair with a blue wire and taped back on the frame at the rear. They are taped up at the firewall under the brake booster too. The orange wire is pre-terminated with a ring to fit on the studs at the back of the electrical center. Put the wire on the stud and install a fuse for the correct stud.

[kirkRHughes]

The bone head that installed my cap wired the interior light to the parking lights. Now if I want to turn on the lights to see in there I have to go up front and turn on the parking lights and listen to the dinging. If I wasn't so lazy I'd rewire it.