Installing a Fused Distribution Box and Power Inverter
Date: 8/30/03
By: Bob_98SR5

Summary
Installing a fused distribution box (hereinafter known as "FDB") will allow you to have a "distributed hub" of uninterruptible power to a variety of electronic devices. If this sounds familiar, it is very similar in concept to a computer router connecting multiple computers in an office---only with electricity. For example, I purchased a four-position FDB that currently powers a 400W inverter and will later power a 4-channel amplifier. I have the flexibility to later add two more devices to this FDB.

I also found some good information at sounddomain.com's forums and at this website. For the last website, click on #14 - Fuses and understand every thing on that page. The key learning point is to make sure you understand the theory behind fuses, its relationship to power cable gauges, and how it relates to the amount of power your system can carry.

To reiterate, I do not recommend you continuing unless you completely understand the theory behind it and here's why: if your power cable gets overloaded for whatever reason, there is a high probability your power cable will "catch and burn" on its entire length. That could cause quite a fire inside the cabin of your 4Runner---not good. But properly planned, the chances of this occuring will be virtually non-existent.

Here's the master diagram for this writeup.

Step 1: Removing the Panels
First, open your hood and disconnect both the positive and negative terminals on your battery. Next, open your door and begin removing the lower driver's side panel, kick panel, step plate, B-pillar trim panel, and rear step plate. You'll need to use a 10mm socket and your cordless screwdriver to do all of this.

Remove the four 10mm bolts (4) at the locations marked above. I recommend removing the entire panel out by unscrewing the hood and gas tank release latches (S) with your philips-head screwdriver		After removing (A) which is the same thing as the pic on the left, snap off kick panel (B) and unfasten step plate (C), which is held down by philips-head screws

You'll also need to get the driver's side lower B-pillar trim piece out of the way as well as the rear driver's side step plate. The B-pillar trim piece is held to the 4Runner with snap rivets and is easily unfastened by pulling it off. The rear step plate is also easily removed by unscrewing the screws with your cordless screwdriver.

As you can see, there are only 3 snap rivets holding this piece to your 4Runner		Remove screws (S) and remove this step plate

Step 2: Drilling Your 4 AWG Power Cable Hole
Most people would probably advise you to just punch the 4 AWG power cable through the existing firewall boot. However, this is a pretty thick cable---0.232 inches (5.9mm) in diameter. For more information on AWG sizes, click here. Thus, I decided to take a drill bit slightly larger than 0.232" (sorry folks, it's been awhile since I did this) and drilled a new firewall hole to accomodate both the 4 AWG and a nifty little 4 AWG grommet too:

Here's a close up of the screw-in grommet that protects my cable as well as from water. I highly recommend it!		Here is a shot of a rubber grommet (G) that I used to test fit the grommet to the left. Note: the leftmost firewall hole with the red wires coming out of it is from my 12v aux fuse box (see Step 6)

Make sure you center punch the hole, use plenty of tapping oil, and gradually move up drill bit sizes until you drill a hole that will accomodate your grommet.


Step 3: Connecting Your Battery To Your ANL-Fuse Box
The first task we need to do is to create a short, 12-inch (or less) positive power cable that runs from your secondary positive battery terminal (1) to the ANL fuse box. To start, mount and screw down the ANL fuse box to the top of your 4Runner's fuse box (F, pictured below). Measured a length of 4AWG cable from the secondary positive battery terminal to the left side of your ANL fuse box. Give it an extra inch or two, just in case. Next, cut about a 1/2-3/4" of the protective covering off each end of your positive power cable and screw on two O-ring connectors to each end. To finish, screw down one end of this cable to the ANL fuse box and the other end the secondary positive battery terminal.

Connect the 4 AWG cable by unscrewing nut at (1) and your negative ground cable at point (G). Mount ANL fuse holder at point (F). Refer to pic on the right		The base of the ANL fuse holder case is screwed onto it (F, at right) with self-tapping screws (S). Note: the gold bolts are where the ring connectors and the ANL wafer fuse is mounted

For the negative ground cable, follow the same procedure above, making sure that you strip one end bare and the other end with a ring connector. Of note, because the negative (stock) battery terminal (metal part) was crimped onto the existing ground cable, completely cut it off and use an aftermarket battery terminal. This will allow you to crimp on the much thicker 4AWG ground cable you just made to the 4Runner's ground battery cable. Begin by crimping the bare end of your new 4AWG ground cable and the existing negative battery cable inside your new battery terminal. Finish by unbolting the 8mm ground cable bolt (G, above) and fasten down the 4AWG (ring connector end) ground cable to it. For now, do not fasten down your ANL fuse yet. We'll save that for the end.

This is the cable from the (+) battery terminal to one end of the ANL fuse holder. Notice the two different kind of O-ring connectors used. The one on the right came attached with the original, raw cable (reused)		This is the stock negative battery terminal (C). As you can see, ground wire (N) is crimped into it and needs to be upgraded. Cut it off at the intersection (X), discard (N) and crimp in your new 4AWG ground wire and the battery ground to your new neg terminal.

Now find a good place for your FDB. I placed mine below the right passenger seat in the area where the pouched tire iron exists. Do a dry test fit and then lower your seat to make sure you can close the seat down without interference. When you are satisfied, screw down the FDB with self-tapping metal screws.

Here's a close up of the FDB itself. Points (A) represent the slots for the four AGU fuses. Points (S) represent the holes for your self-tapping metal screws		As you can see, I removed the tire iron kit (T) from this area. (U) is the uncut, raw 4AWG cable and (4) is the FDB dry-fitted and ready to be screwed down with self-tapping metal screws

Next, connect a screw-down type O-ring connector to one end of your 4AWG power cable and attach it to the other end of your ANL fuse box. Then run the other end of this long power cable from the ANL fuse box, through your new firewall hole, down behind the driver's side kick panel, along the side step plates and to your FDB. Mercifully, the white plastic wire holders are just large enough to accomodate the 4 AWG, so thread it through them.

Run the 4AWG through the firewall and behind this black rubber boot		Run along the kick and step plates and through the white plastic wire holders		Run the 4 AWG cable up and under the rear passenger carpet to the FDB (F)

Step 4: Connecting Your Power Cable to the FDB
Run the 4 AWG power cable to the FDB. Strip an appropriate length of the protective covering off (I recall its about 1/2" to 3/4" for mine). Next, use an allen wrench key to unscrew one of the 4 AWG (input) allen screws out. Insert the 4 AWG power cable in and tighten down the allen screw to secure.

Here's a shot of the 4 AWG power cable (4) inserted and fastened down to the power inverter. Please note that I ended up screwing the FDB down (S) *over* the carpet, not under it, as this picture shows.		Here is a shot with the protective cover on with an AGU fuse installed. Points (8) are the four available accessory power outputs. We'll run a power inverter to one of them. Note: unlike this picture, do not install the AGU fuse in yet

Step 5: Connecting Your Power Inverter to the FDB
Begin by creating positive and negative 8 AWG cables for your power inverter. The length of each cable will be determined by where you want to mount it. I decided to mount mine in the rear cargo area. For the positive cable, strip about 1/2" to 3/4" of the protective covering off both ends and crimp a 3/8" ring connector to one end only. Screw down that 3/8" ring connector to your power inverter input. Next, use your allen key to remove the FDB's 8 AWG output screw, insert the bare 8 AWG power cable into it, and then tighten down.

Here's the 8 AWG positive cable hooked up to the FDB		Here's both positive and negative 8 AWG cables screwed down to the inverter

For the negative negative 8 AWG cable, strip about 1/2" to 3/4" of the protective covering off both ends, and then crimp on a 1/2" ring connector on one end and a 3/8" ring connector on the other. The best location to ground it for my install was the seat belt bolt. Begin by lifting up the carpet and use a 14mm socket w/ extension to remove this bolt. Next, place the 1/2" ring connector down and then thread/tighten down the bolt. This will act as your ground. Next, connect the other end (3/8" ring) to your inverter.

Here's a shot of the both ends of your negative 8 AWG ground cable. The smaller (left) one connects to your inverter while the larger one (right) connects to your seat belt bolt		Lift up the carpet in the right passenger seat section, unbolt and then secure the 8 AWG 1/2" negative ring connector down

Step 6: Connecting And Testing Your Power Inverter to the FDB
Insert both the ANL fuse and the AGU fuses into their respective fuse holders. Plug in some device such as a small stereo into your inverter. Flip the "ON" switch on the inverter and turn on your stereo. Of note, mine did not work the first time. After I drove to the market and tested it again did it work. I presume that maybe the inverter needed to have some stored energy in it. I am not positive, but that was my observation. If anyone knows the technical reason for this, write me.


Hit the "On" switch and boogie

I can't tell you how much I enjoy using this mod. Once or twice I've made an excuse to leave the office, taken the ol' 4Runner down to the beach, put a few coins in the meter, and did some work on the laptop.

- The second hardest part was sourcing the parts at a reasonable price. I was quite disappointed to find out that none of the Radio Shacks had anything like 4AWG cable or 1/2" ring connectors. I ended up purchasing many of my parts from eBay, Waytek and Sounddomain.com. One place I do not recommend is Pacific Stereo in El Monte--let's just say I would never go back to this place.

- Because I didn't have access to a large crimper, I ended up using my vice to crimp down some of the connections.

Questions or feedback? Email me and I'll try to get back to you. If this article helped you save time, money or just made things more convenient for you, please consider donating to keep this site alive.