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Discussion Starter · #1 · (Edited)
Here is a simple guide to the wiring connectors and terminals used on our Dodge Ram trucks. FCI makes a family of connectors called Apex. These Apex connectors are used in Chrysler, Ford and GM vehicles. These are also used on farm equipment, generators, and in other harsh environments needing a reliable connection system. If you plan on adding wiring to your vehicle or equipment, read this because it will save you a headache down the road. These connectors can be weatherproofed with seals around the joint of both connectors and seals around each wire. Unused terminal slots can be sealed with a plug.

This information took me a year or so gather. When I started creating my custom ignition system, I needed a way to tap into the existing wiring in a clean and reliable way. I originally used a 12 way Molex connector which did the job but not near the quality that I wanted. I refuse to use t splices or crimp connectors on this sort of thing. Now that I found all of this information, I want to share it with others who may have the same intentions that I had or that need to replace a few things.

To start off with, here is a link to a PDF file that explains the FCI Apex connection system. This guide contains just about all the information you need, including how to assemble/disassemble connectors (you need needle nose pliers) and a description of the terminals with part numbers. This guide is what you need to read first.

There are only a few different sized terminals as you have probably noticed. The average size is the 1.5mm terminals and those pesky burnt ignition wires use the 6.3mm terminals. There are also 1.2mm terminals.
The Apex connection system is very reliable. The female pin is the key, the image below explains how the female pin is designed.

The male pin is forced down by the pre-loaded spring (the gold part) which creates a large contact area on the raised rib contact surface. Also the connectors keep the terminals in-line with each other. The design of the connectors and terminals greatly reduces the force required for connection. If you compare the force between my original 12 way Molex and my new 14 way Apex connector, it is amazing how easy these Apex connectors connect. I now do not like Molex connectors.

Now here is an overview of the wiring I changed in my truck for my ignition system. I ran a 14g. wire from the fuse box, through the firewall passthrough, to the center console to power my ignition system. It is connected to a 20 amp fuse, I don't plan on using more than 5 amps but in the future I may need some extra power for something. I also have a computer in place of my radio and I may end up powering the computer with this as well. The computer monitor (where the radio used to be) is rated for 7 watts and the computer has a PSU rated for 150 watts. It uses almost no juice since its atom based.

Alright, the first thing I had to do was trace out an unused circuit in my fuse box for this use. Since there is only 1 free slot for power all the time, I didn't have much of a choice. So I installed a 20 amp fuse into fuse #2, created a jumper out of a mini-fuse, and then added my new 14g. power wire to the fuse box.
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The above picture is a pin out of the relay as you see it in the fuse box, keeps things simple. Sort of a visual of how the power runs through them as well. The picture with the multimeter probe is the pin that I tapped into. Since for some reason my fuse box does not have a normally closed circuit, I had to jump the relay coil signal and run my power through that. Not how I really wanted it but I might change it in the future if I am pulling much more power through this circuit. In order to run this how I want, you would have to get a relay that has opposite NO/NC circuits or install a normal relay and then power it to connect the circuit. This might be confusing, I know. The jumper is simply a mini-blade fuse that I broke and pulled the pins out of. I then soldered a wire to the two pins and covered it with a heat shrink. The mini-blade fuse pins are the same size as the relay pins, instead of destroying a relay I chose a mini-blade fuse.

Now my ignition system is basically a set of relays that replaces the ignition switch. The steering wheel lock is still enable so I still need the key in the ignition for full operation of my truck. I did remove the shift lock though. A good guide to correct pin crimping can be found here. A good crimp is critical. That guide also explains about crimp tools. FCI has their own crimpers, but so does Molex. I bought myself a brand new pair of the cheapest crimpers I could find. Cost about $15 off of google shop, they are Waldom/Molex crimper WHT-1921. I have used these to crimp hundreds of terminals, both Molex and Apex ones, no problem with either. Whatever you do, do not use pliers and simply bend the terminal legs over and expact that to hold the wire because it will not and never will. Get the right tool.








I did have my dash out completely when I did this, fixing other issues and thought, what a great time to do this! I had a bunch of spare wire, most of which was the same colors/size of the factor wires. My method of installing this connector was not the simplest. I cut all the wires to the same length, gave myself plenty of extra room as you can see. The plug in the above picture has almost an extra foot of wire, between both male and female plugs. Then I stripped about half an inch of insulation off of them. Now for the hard part. I took an exactoknife/razor blade and then cut the insulation around my target wire. I stripped off about a half an inch of insulation from the target wire, wrapped the wires then soldered them. I decided on this method over cutting and spicing three wires because I have no idea. I then wrapped these joints cleanly in electrical tape and then wrapped the whole wire loom in electrical tape as you can see. The finish is very nice and very functional.

The price for these connectors is not the cheapest. I bought a 14 way and a few 4 ways for my whole ignition system. They were all sealed as well. Each connector is about $3-7, and the terminals are anywhere between $0.07-0.15 each. Mouser is where I bought everything from. Mouser is pretty much the only place that I have found that sells these, not even eBay has them! Terminals can be expensive as well, some can be almost $2 a piece. Some are gold plated, some are made of various materials and whatnot. Gold does not corrode so you decide. I bought the cheap ones, paid about $0.08 for all of them.
 

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I have an 04 with 6 or 7 spare relay slots. I want to install my gauges and I want to use factory fuse box. The spare relay holes already have pins in them. Where does the load wire go to? Does it go to a plug underneath the pdc? If so what terminals do I need to Hook up my wire for ignition hot for my pyrometer? Can you give me all the terminal part numbers? I want a nice clean install.
 

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Discussion Starter · #4 ·
There is a picture in my original post that shows the pin numbers on the relay socket. I realize now that it might be confusing to some. If you pull off a relay and look at the bottom of it, there should be numbers stamped next to each terminal. Pins 85 and 86 are for powering the coil. Pin 30 should have 12 volts and pins 87 and 87A are the load wires. The factory fuse box does not offer much for expandability. There is only 1 slot for a fuse that I found. This fuse then powers pin 30 of a few relays, which is why I jumped a relay socket. Most of those relays do not engage with the ignition key, so you would have to manually wire in another relay to engage it with the ignition key, or have a switch engage them.

How many items are you looking to add? Just one power wire like I did? If all you need is 1 power wire then follow what I did. However, since you are adding gauges, you probably want power only when the ignition is on, which means you will need to trace some of the pins in the fusebox. Your best bet is to remove the fusebox/PDC, don't even try to do this with it in the truck as it will make it so much more difficult.

In order to add these terminals to the fusebox/PDC, you will have to add the terminals to the plugs under the fusebox. Remember, there are multiple sizes, so you have to determine which size terminal you need. Once you get the fusebox off and you look at the pins, you can cleary see there are 3 different sizes, so its easy.
 

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Here is what I did to accomplish the same thing (I think):
I used a couple of 6 fuse blocks, a relay, relay socket, and a tupperware box. I mounted the tupperware box right on top of existing fuse box lid (it flips up to open that lid). In it I mounted the 2 fuse blocks, one of which I provided power directly off the main source for the fuse box below, and one of which I fed through the relay which is triggered by a source using one of those bussman taps from a key-on circuit below.

So now I have 6 always on fuses, and 6 key-on fuses. For convenience I also mounted a ground bus in the same location.

My total cost was about $12 but I already had the relay, tupperware, odd wires and connectors. It really cleaned up my underhood area and made all my fuses accessible in the same place.


There are pics in this thread:
http://www.cumminsforum.com/forum/3...58591-accessory-underhood-wiring-harness.html
 
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