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Thread: Wiring Harness Through the Firewall

  1. #1

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    Wiring Harness Through the Firewall

    I am at the wiring stage. What, if any, are the alternatives for drilling three, 1 1/4" holes in the firewall for the wiring harness per the Ron Francis instructions? If this is the only and best way to go, so be it!

    Thanks

  2. #2

    Steve >> aka: GoDadGo
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    If you are installing the fuse block where Factory Five designed it to fit, then I cannot help you.

    If you want to move it to the passenger side of the car then this is what I did:


    1 I moved my the fuse block to the passenger side of the car (MK-4) which saved room in the pedal box area but it was a bit of a pain in the neck.
    2. I went through the top of the transmission tunnel and the lower firewall which was another pain in the neck.
    3. I hid my through bulkhead penetrations behind my switch panel/stereo console that I made from some aluminum kick plate.
    4. The only thing (wire) that had to extend was my brake light switch; however, I did have to flip the blinkers from left to right since my front harness now goes forward via the passenger side upper body support.
    5. While this was a bit tough to do without any major modifications to the harness, now the fuse block should stay quite dry, plus I can get to my pedal assembly a lot easier than most folks.
    6. An added benefit is that it makes it easier to get to the windshield bolts on the driver's side of the car.

    Non-Traditional Fuse Block Location:
    http://thefactoryfiveforum.com/attac...2&d=1458496655

    Switch/Stereo Console Pic:
    http://thefactoryfiveforum.com/attac...4&d=1458505006

    You Can See How I Routed Stuff In This Video:
    https://youtu.be/_wnHDNgnNqs
    Last edited by GoDadGo; 10-06-2017 at 11:17 AM.

  3. #3
    Seasoned Citizen NAZ's Avatar
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    I used two American Autowire 22-Circuit Bulkhead Connectors that are much like you would find as OEM bulkhead connectors on any car coming out of Detroit. I purchased mine from Summit Racing for $37.80ea, part number AAW-500666. These are Weatherpack style and be advised you will need the Weatherpack crimpers. I also label all my wires with a label maker that prints various sizes of shrink tube labels. All this can get pricy if on a short budget but this is what it takes to make a professional looking wiring installation.

    Also, I did not use that Ron Frankenstein wire harness as it is way too messy looking for my taste. I elected to wire from scratch which is way more work assembling all the necessary plugs and sockets and pins required to roll my own. I hate splices so had to have all the correct connectors. But you don't have to do all this extra work to make a decent looking through the firewall installation. Just cut your wire harness and connect it with the bulkhead connectors above.

  4. #4
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    I ran the engine/starter pigtails down thru the left side tunnel with looms clamped underneath the 2" tube. Accessories and ignition were routed to the right side thru the blank plate for the far right side small bulkhead plate thru a large oval grommet I had. My ignition module is inside firewall right side.

  5. #5
    Senior Member Dave Howard's Avatar
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    The MkIV used to come with a vertical slot cut at the top of the inside drivers side footbox. The vertical aluminum piece that angles in towards the transmission. The slot was at the top of the piece at the firewall. I used this location for some of the Ron Francis wires that exit from the fuse panel area. I also used an opening behind the dash on the far right. This location is documented in the assembly manual. This kept the firewall clear and clutter free.

  6. #6

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    Thanks to you all for the input. It's all a great help!!! Joel

  7. #7
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    I drilled one larger hole and uses a nice seals it grommet from summit racing that Rivera into place.

  8. #8

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    10L Cobra can you send a picture??? Thanks

  9. #9
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    Following. I’m in the garage now staring at my nice firewall and wondering if there is a better way. LOL
    FFR8551 289 FIA build in progress.

  10. #10

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    I think there is a better, cleaner looking way. Lots of advice above and it's all good. I took bits and pieces of several of the suggestions. Here's what I did.
    Fuse panel is in the standard location. I ran the alternator and starter bundle through one 1 1/4" hole in the Center Dash Support space. This is that rectangular section of aluminum, center and below the firewall. I also ran the gauge cluster/electric choke bundle through another 1 1/4" hole in this space. I ran the rear harness through a 1 1/4" hole in the transmission tunnel cover and then per the directions along the driver's side chassis member. Wiper and heater bundle exit to the far right in the existing cutout and the front harness bundle per the directions through the front of the driver's foot box. In my car, the dash support piece is covered on the front and sides with a piece of fabricated aluminum and so none of the wires are visible. I will have a battery disconnect and a couple of switches mounted there. Joel

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