Power through the Firewall (Gen 4)

Discussion in 'Gen 4 Prius Accessories and Modifications' started by William Redoubt, Sep 11, 2016.

  1. William Redoubt

    William Redoubt Senior Member

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    I finally started to move separate, fused power into the passenger compartment. My eventual goal will be to provide power for a 750 watt inverter both in the front seat and under the hatch (700-watt coffee maker and 700 watt microwave), as well as induction based trailer lighting (Tekonsha 110250 T-Connector, no cut, induction based).

    After reading Gen 3 methods, I followed the same procedure, with some changes. There is a large rubber grommet with a wire bundle just to the left of the accelerator. I used a Phillips head screwdriver to pierce the grommet on the left side, and used a fish tape to pull a "pull string" from the engine bay into the interior. I pulled the wire from inside the car into the engine bay without any issues.

    To make it easier, I removed the left kick panel and the plastic under dash panel. One plastic "nut" and two screws.

    The whole process took about an hour.
     
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  2. dmanp84

    dmanp84 Junior Member

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    You wouldn't happen to have any video or pics of your endeavours?

    Posted via the PriusChat mobile app.
     
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  3. William Redoubt

    William Redoubt Senior Member

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    No. Sorry. But it is rather straight forward. Have a good flashlight on hand.
    1. Remove the rocker panel trim by pulling it off (has clips only).
    2. Remove the kick panel by removing 1 plastic nut (fingers only -- it's not tight) near the brake pedal and pulling on it.
    3. Remove "modesty panel" by removing two phillips-style screws and fiddling with a single tab under the steering wheel.
    4. Lay on your back over the rocker panel and look above and to the left of the throttle linkage. There will be a large encased wire bundle running through the firewall at an angle running from left to right. The grommet is quite a bit larger than the encasement of the wire bundle and the encasement provides lots of protection for the wire bundle itself.
    5. I pierced the grommet on the left side, pressing the screw driver through at an angle pointed toward the location of the battery, and then used a standard electrician's fish tape to get into the engine bay. I then pulled a "pull string" (a pretty stout piece of nylon braided cord) into the cab.
    6. I attached the wire the the pull string and pulled it through. I used 2 strands of #12 braided wire from Lowes. 25 feet is sufficient. Make sure you "streamline" the attachment to the pull string to make the bundle as small as possible. You can also use a bit of lube to make it slip through easier.
    7. Pull the wire through. That's it! Very simple. The biggest challenge is to get the fish tape through the mess of pipes and tubes between the engine and firewall. For me a couple of twists and push/pull and it popped right out into the clear.

    Initially I was going to use one of the strands for positive and one for negative, but after running a calculation on the amperage draw for a 750 watt inverter on the approximate length of the conductor, I used both for the positive and picked up the ground on the chassis.

    I am installing the outlets today (hopefully). My setup will include two switched cigarette type adapters with dual usb outlets and a set of terminals for hooking up the inverter using jumper cable-style clamps (they came with the intverter). I am using an illuminated-style rocker switch so I know when the setup is "hot". I 3-D printed the face plate for the outlets and will be doing the same for the blocks for the terminals. The outlets will be high on the interior trim above the left rear tire. The terminal blocks will be installed low in the cutout bay near the floor.

    The whole setup will be fused at the battery and hot to the back so I can install my trailer light converter which is coming this week.
     
  4. Owll

    Owll Junior Member

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    Good write up. I went the "other" way. There's another firewall penetration on the passengers side, but it's probably more difficult to get to. You have to remove the glove box; the kick panel and unscrew the white colored electrical junction to the right of the cabin air filter assembly. There's just enough room to slide a fish wire through the penetration, and grab it from the engine compartment.

    The circuit I ran was for a ham radio transceiver. The radio itself is under the front passenger's seat, and the head unit is attached immediately under the shift lever.

    It would have been much easier if I was 30 years younger!
     
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  5. Locksmith

    Locksmith Member

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    How did you mount the control head? Any pictures? This is my next project.
     
  6. G23

    G23 Junior Member

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    Is the grommet you are talking about the one with a nub sticking out of it (on the right side of grommet when view from engine side)? How did you seal the grommet around your wires? If you used a knife or screwdriver, I would imagine it would tear a little rather than make a round hole. the hole might get bigger over time. Thank you
     
  7. William Redoubt

    William Redoubt Senior Member

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    I poked a hole. Not concerned about it getting bigger. I have been watching it. Seems ok.
     
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