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Ultimate wire through the firewall

Discussion in 'Technical Chat' started by Backinblack03, Mar 22, 2013.

  1. Mar 22, 2013 at 6:59 PM
    #1
    Backinblack03

    Backinblack03 [OP] Well-Known Member

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    ABS? What ABS?
    I've had this particular setup in at least the last three of my vehicles, and works great. Thought I'd share before I install it into the truck...

    I have a length of 6-conductor, shielded 18awg cable and a Skintop PG-11 bulkhead fitting. First I find a safe place to punch a ¾" hole in the firewall. Usually with a pilot and then a step drill. Then I fit in the PG-11 and tighten the self-sealing nut down. This provides me with a safe way to pull my cable through. The PG fitting will crimp down on the wire and seal it up from the elements and provide strain relief.

    I then can attach whatever I need to for lighting controls and sensor inputs through the firewall without having to run multiple wires multiple times. I usually then terminate the cable with spade connectors, or to a terminal block on either end, in a dust-proof box of sorts.

    Works great for control circuitry of auxiliary lighting, remote start sensors, security sensors and whatnot.

    [​IMG]

    [​IMG]
     
  2. Mar 22, 2013 at 7:14 PM
    #2
    FFTacoma

    FFTacoma Member

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    Are the individual wires just for handling low amperage? By "control circuits" do you mean these wires actually terminate at a relay that handles the higher amperage. Thanks for posting. Your weather tight connection looks like it would work better than a rubber grommet in the firewall.
     
  3. Mar 22, 2013 at 7:16 PM
    #3
    Fractured

    Fractured FPS-a-holic

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    depending on what type of wires those 18 awg are, they can handle 16amps at 90c (THHN)
     
  4. Mar 22, 2013 at 9:30 PM
    #4
    llibrm

    llibrm Well-Known Member

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    Those look like wire and a cgb from a flow meter. Industrial water treatment freebie...?
     
  5. Mar 23, 2013 at 7:02 AM
    #5
    FFTacoma

    FFTacoma Member

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    Fractured.....Thanks for clarifying.(Noticed your IBEW emblem....was in that union out here, too) I totally overlooked that it says its 18g wire in the write up. I was thinking that was a Cat-5 cable with the super small, low amp wire. I have a quite a few electrical accessories I want to add and that's the way I want to wire my circuits. I am running Cat-5 wire into the cab. The higher amperage wire is all going to be out under the hood, etc. The Cat-5 will go out to a relay box, using the relays to switch the higher amperage end of the circuits.
     
  6. Mar 23, 2013 at 7:33 AM
    #6
    Failure2Comply

    Failure2Comply Well-Known Member

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    OP, if you use the single, unshielded, stranded wire in the cable (the "drain" wire) only connect one end to ground or it will set up an FM Antenna effect. Shielded cable is used quite a bit in communication and control wiring so the induced signals from the "FM Effect" plays an important role. The bulk head connector you chose is a great choice and they work extremely well.

    Even though THHN rated wire (Thermoplastic High Heat Nylon) is rated for 90c, you have to go by the connectors which are the weakest link. Typical terminal blocks, wire connectors, fuse boxes, and disconnect switches are rated at 60c/75c. So when sizing wire select the 75c column for true amperage rating to meet codes and for wire and component longevity.
     
  7. Mar 23, 2013 at 9:56 AM
    #7
    Backinblack03

    Backinblack03 [OP] Well-Known Member

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    ABS? What ABS?
    I used to participate in the design and building of industrial automated control panels that utilized both digital and analog signaling. The drain is typically connected at the source of the signal, and the other end cut flush and heat shrunk to the jacket. It's all good... :)
     
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