Tips for Running Wire through the Firewall

  1. robmoz

    robmoz Member

    First Name:
    Rob
    Vehicle(s):
    2018 Wrangler JLU Sport
    Joined:
    Nov 18, 2018
    Location:
    Chantilly, VA
    Posts:
    16
    Liked:
    26
    I installed Oracle Halo lights a few weeks ago along with their LED headlight bulbs. I like the halos a lot. They are very bright, but be aware they are definitely have a bluish-white color.

    I have a Sport, so no DRLs. I tied the halos into the heated seat fuse using a fuse tap. That port gets energized when the ignition is on, giving DRL-like operation. However, I realized there are times when I want the engine to be running but have all the lights off, so I decided to add a switch for the halos at the bottom of the dash panel below the headlight switch. As has been pointed out in numerous posts, running the wire through the firewall is the hardest part. I found a good bit of information on the forums, but I still ended up having to figure some stuff out. I thought it would be helpful to provide some lessons learned, specifically on how to run wiring through the firewall.

    I have a manual transmission, so running wire through the hole where the clutch pedal would be was not an option for me. I went through the grommet that is used for the large cable bundle on the high right side of the passenger footwell.

    First, remove the passenger seat. If you can do this job without taking it out, you are a lot smaller and/or more flexible (and maybe smarter) than I am. It really wasn’t that hard and it definitely made access easier. Just remove the 4 bolts (Torx driver bit), lift the seat up, turn it 90 degrees towards the driver’s seat, and tilt it forward. Be mindful of the wiring connected to the bottom of the seat. Remove the two connectors from the cable harness to the seat and pop the two retention clips for cable management out of the bottom. You can then pull the seat out of the Jeep. You can probably remove the glovebox instead of the seat, but taking the seat out gave a lot more room to work.

    Stick your head into the passenger footwell and look up to the right. You will see a large black bundle of wires feeding through a black rubber grommet into the engine compartment. This is where you will poke through.

    Footwell with grommet just out of view on top right (red wires running towards it):
    111.jpg

    Close up of grommet from the inside of the Jeep:
    112.jpg

    You should then look on the engine side to see where the wire will come out. Get under the Jeep just behind the passenger side front wheel and pull back the fender liner to access the engine compartment side of the grommet. You do not need to remove the fender or liner. The liner is very thin and flexible and is easy to pull aside.

    Engine side view of the grommet (laying on my back looking straight up with the fender liner pulled back):
    113.jpg

    I made a small hook on the end of a straightened coat hanger and looped a wire through it and attached with a little duct tape. I then cut a small slit near the bottom of the grommet on the interior side of the grommet and pushed the hanger in. It would only go in a few inches and then hit resistance. Also, I couldn’t see anything poking out the other (engine) side of the grommet. I then had my daughter push the hanger from the inside and while I looked and felt from the engine side and realized that there was a second wall to the grommet that the hanger would have to push through as well.

    After realizing this, I changed strategy and just used a pointy-ended coat hanger with no loop and taped the wire a few inches from the end. My daughter then pushed again and the tip of the hangar could easily be seen trying to get through. I told her to push a little harder (insert labor-oriented dad-jokes here “Push! Breathe!”; she wasn’t amused) and it popped through. It was then easy to grab the end of the hangar with pliers and pull another 6 inches through. I then used wire snips to cut off the rest of the hanger on the interior side so I only had to pull a little more of it through. After that, the rest was very straightforward.

    I also ended up pulling a couple feet of another spare wire through so if I ever want to run wire through again, I can just tie it to that wire and easily pull it through. Hope this helps someone!
     
    Darter02, aah78, zyt and 11 others like this.
  2. me109stock

    me109stock Active Member

    First Name:
    Martin
    Vehicle(s):
    2018 JLU Rubicon 6-Speed Manual; 2008 Ford F450; 2003 Porsche Boxster S
    Joined:
    Sep 10, 2019
    Location:
    Linden, CA
    Posts:
    37
    Liked:
    22
    This should be tied to several other posts! Exactly what I was looking for trying to wire my Rock Slide Engineering Gen II Steps. It's a shame so many people drive automatics these days...

    I'm very tempted to wire through a single set of heavy gauge POS and NEG wire and just install a fuse block inside for all my future interior power needs.
     
    zyt likes this.
  3. Boutch76

    Boutch76 Well-Known Member

    First Name:
    Yannick
    Vehicle(s):
    2018 Jeep Wrangler Sport JL 2D Manual
    Joined:
    Oct 15, 2019
    Location:
    Vancouver
    Posts:
    77
    Liked:
    51
    I am in the process of passing wires the circumference of a dime in this location and its pain in the ass. So much crap falling on my face. I have been trying to figure this out for a couple of hours now. I really wish they would have made it much easier for the manuals.
     
  4. vavaroutsos

    vavaroutsos Well-Known Member

    First Name:
    Pete
    Vehicle(s):
    2015 Sprinter Crew Van 2500 High Roof 144" WB OM651 Brilliant Silver, 2019 JLR 3.6L 6SPD Granite Crystal
    Joined:
    Nov 24, 2017
    Location:
    Scotts Valley, CA
    Posts:
    539
    Liked:
    310
    Remove your fender and wheel liner. Get a few replacement clips from Amazon or someplace in case you break one. Don't blindly poke wires through the boot. The harness is not wrapped within the boot. It's like a rats nest and is easy to damage a wire. Once you get a clearer view of the boot, you will see there is a nipple on the upper portion that looks like it was meant to be cut off to run new wires through. That being said, I don't think you are going to fit wires the size of a dime through here. Why do you need such heavy gauge wires inside the cab?
     
    Boutch76 likes this.
  5. 1996cc

    1996cc Well-Known Member

    Vehicle(s):
    19 JKUR
    Joined:
    Aug 20, 2019
    Location:
    Oregon
    Posts:
    172
    Liked:
    97
    Boutch76 likes this.
  6. Boutch76

    Boutch76 Well-Known Member

    First Name:
    Yannick
    Vehicle(s):
    2018 Jeep Wrangler Sport JL 2D Manual
    Joined:
    Oct 15, 2019
    Location:
    Vancouver
    Posts:
    77
    Liked:
    51
    Thank you for the tips. I installed a Rough Country switch panel. It's either I was making a inch and a half wide hole or one the size of a dime.
     
  7. blnewt

    blnewt Well-Known Member

    First Name:
    Brad
    Vehicle(s):
    2019 Jeep JL Sport S, 03 Toyota 4Runner, Infiniti G37, Toyota T100 (Retired 74 CJ-5, 80 CJ-7)
    Joined:
    Oct 8, 2018
    Location:
    New Mexico
    Posts:
    1,591
    Liked:
    1,353
Loading...

Share This Page