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Electrical Advice - Wiring More 12v Sockets

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Hey y'all!  I'm planning to wire some additional 12v sockets in my rig.  I'm not an electrical engineer and could use some advice.  Actually, I could use more than a little advice.  Could someone help me build a plan?


  • One on the left of the steering wheel for me to charge a cell phone or GPS or something that may be on the left side of the windshield.  This one may actually be one of those dual usb voltmeter things.
  • One inside the console for a CB
  • One on the passenger side of the console
  • One or two in the cargo area.


I was thinking that I would run one red wire (what gauge here?) from a fuse box the engine bay to a new little fuse box under the dash somewhere.  


I guess it would be best if this was on a relay.  I think I'd like a switch on the inside that turns on all them all on and off.  That way I could have things on with or without the ignition being on.  For simplicity, I could put that relay inside the cabin couldn't I?


From there I could run a smaller wire (what gauge here?) to the sockets. Does each socket need it's own wire to the fuse box or would I have two or three on each fuse?   I guess the wires to the cargo area should be a little larger too.  For grounds, I thought I would find a screw somewhere relatively near the socket.  


It should probably also plan out anything else right?  I also want to mount some led lights inside the hatch so they would shine down on the area when the lift gate is up.  I was thinking about something like these:




For the interior fuse boxI was thinking about a block similar to the one below.






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I think much of what I replied to on your original light bar thread applies here to some degree.  For this particular thread, I might also make the following suggestions:

  • In regards to wire gauge, start with Power = Volts x Amps, or P=VA.  Figure out amp draw first (A = P/V), then you can use a variety of wire gauge charts.
  • Wire gauge, part 2: the length of wire matters, too.
  • BTW, I don't recommend those pod lights for that application: too much amp draw for the application, blinding light, very bulky, heat generation, limited space.  At 140W, they'd warrant 10AWG (max 15A) because of the 10A-12A draw (140W/14V = 10A, 140W/12V = 11.7A), exceeding 12AWG (9.3A max), but because they'd need about 20' of wire, you might even consider 8AWG...a bit heavy duty for the application, though.  Having installed flush mount lights under my liftgate (see below), there's not much room to work with unless you're willing to cut metal.  Unfortunately, there aren't a lot of low profile flush mount LED options out there.  The adhesive LEDs aren't aesthetically appealing, but are great functionally.
  • Plan on separating your power needs to front vs. back, if you haven't already.  That way, you can run dedicated leads to each area with a thicker gauge wire, then distribute power on thinner gauge wires.  This will spare you a lot of headache routing wires.
  • The cheap USB/Voltmeter/Socket combos that you can find everywhere on Amazon and eBay are great, inexpensive ways to add those items anywhere.  All they need are two wires (and can be daisy-chained in most scenarios) and a 1-1/8" or 1-1/4" bit.  And there are tons of options available.
  • Consider your circuit demands when thinking about relays and switches, as one or both might not be necessary.  Generally speaking:
    • You really only need a relay if the max amp draw on the circuit will exceed the max amp rating of the switch, or if you want the circuit to energize in the ACC/ON positions.
    • A switch, of course, is only if you want/need manual control.  If worried about draining your battery, you're better off using a relay and ACC/ON lead.  Otherwise, a switch doesn't really offer much practicality unless there's some need (including general safety) to disable all or part of the circuit.  Having it control a light makes perfect sense, of course.



I've done a few projects in my truck that might align with what you're wanting.




Though only an option if you switch to a single-DIN headunit, I bought a factory radio-delete panel and mounted components to it.  Voltmeter, dual USB, and aux audio input pod for the radio.  The voltmeter and USB port tap off the factory power socket.  From Jax99's air compressor setup, the change pocket by your left knee might make for a suitable place to tuck a USB port and voltmeter there.  I'll likely be going back to a double-DIN headunit soon, so those will all get relocated.  (And in case you're wondering, I swapped out the pocket under the radio with one from an All-Mode truck, so that affords some additional switch space, for which there are Carling-sized USB bodies that will fit there.  The All-Mode switch is wired to control my air compressor and lockers.)




This is just a panel kit that came with a switch, voltmeter, socket, and dual USB components.  Wired it up for my fridge.




The panel cover is on a simple harness coming off a 6-circuit fuse panel.  I ran an 8AWG wire from the battery to it.  I intend to run all other cargo accessories and exterior lighting through this.  Also, I don't know if all R50s have that socket in the lower right of the pic, but I think all the trim panels have the flat spot and socket wiring behind it.  You can buy the OE socket, or put any other socket/port/switch there.




The wires come through an existing rubber cap.


As for liftgate lighting...






I really liked these pods, as they're very low profile both above and below the mounting surface, but I wish there was more light output.  The lens is also a switch.  I ran the wire through the OE grommet/boot in the upper LH corner of the gate and over to the rear cargo light, and that's where they draw their power from (yellow harness). 




I just drilled out rivets on the cargo lamp, put in my leads, and riveted it back together.




This allowed the factory switch to act as the master switch for all three pods, then I could turn each on/off as individually.  However, the interior lights will turn off automatically after a few minutes to prevent draining the battery.  You must open a door to get the light back on, but for the liftgate, the door switch is integrated into the latch and is not convenient to toggle.  So, I added a switch (subtly shown below with an unlit blue ring) that toggles the door switch circuit...sorry for the crappy pic, but it's mounted on the plastic bump on the trim behind the pivot for the wiper.



Edited by hawairish
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Looks like Hawairish has you covered! I hadn't thought of putting lights in the hatch, that's a cool mod. +1 for making sure your wire's big enough for everything you'll end up hooking to it.


The fusebox in the first post looks just like what I've got in my engine bay. I used the same 12v outlet as Hawairish used for his rear outlets and it does the job, though I have noticed the cap seems to pop off from time to time.

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I mounted my hatch light to the inside of the hatch hinge, I’ll post a photo when I’m home. It has it’s own toggle. It’s incandescent & I was planning on switching it out for LED but it’s worked fine for 14 years.

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Awesome.  I'll write more later, but thank you.

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