How to build your Own Wire Harness

Building your own wire harness is one of the hardest things to do if you have never done it before.  Ill try to make this as simple as possible for anyone to understand the basic principals of creating your own harness.

I can only give you tips you how to do this, not actually do it for you.  The most important thing to remember when doing this, is, do not rush.  It generally takes a couple weeks for an unskilled person to accomplish this.  Here are a few tips that I have become accustomed to when building your own wire harness.

1. First thing you do is create a plan.  In this plan you will layout the first blue print for your harness. This will include taking all your sensor plugs and cutting them off your old harness and laying them out in front of you so that you can design what you want.  Note that when you are making a new harness you can get rid of SOME of the plugs that you dont really need, like EVAP, A/C controller stuff, etc...
2. Next thing you have to do is layout all your tools to do this. You want to make sure that you know what you have in front of you, and make sure that you have the proper tools.  The tools are as follows: Flux, electrical tape 3 rolls, wire, solder, solder gun, pen and paper.
3. Now that you have everything you need in front of you it is time to compile your own wire harness.
4. Start by going over your owners manual for the schematics(or blueprints) for the wiring diagram. Make sure that you note which wires intersect each other and which wires need ground wires wrapped around them.
5. Compile a hand written blue print for each wire plug.  Make sure that you note the wires ECU location number and if it requires any splicing into any other lines, or requires a ground wire to be wrapped around it.(Some wires like the distributor require ground wires to be wrapped around the outside of the wire to stop any other electrical interference from happening.  Ground wires act as a shield)
6. Once you have composed a list of where each wire goes to, now make another list.  In this list you will make a few short lists.  Your first list will include all sensors that are interconnected together.  For instance your map sensor is connected with the TPS and the EGR sensor.  This will help keep your mind from wandering while working on this harness.  Start with these lists of all the wires that interconnect together, and go from there.
7. Once you have complied a few of your own hand written blue prints, its time to start soldering.  Depending if you are making your own a harness from the ECU or the shock tower connectors can have a large impact on the actual on how long you want your lines to be.  If you are running wire from the ECU to the engine, go for about 5-7 feet per line, depending on exactly where the sensor is located on the engine. For shock tower connectors no more than 3-5 feet are needed.
   
8. Now start laying out your wire for your sensors.  Cut all your wires in your desired length and start following your blue prints.
   
9.  Take your time with this. Do one sensor at a time and take a break.  Having all your electrical connections done right the first time is tricky to do, but with patience it will be achieved.  Start with all the wires that intersect each other.  Tape your wires together for each sensor.  You don't want to have a giant knot of wires when your done.  But do not wrap the harness yet.
   
10. Once you have all your wires run and want to test it out to make sure that all is well, install it on the engine and turn it on to make sure all is well.
    
11.  If everything checks out well move on to the next step, if not read more.  Go back with an OHM meter and check all your wiring again, and compare your own wiring schematics with the owners manual.  Mistakes happen but they can be fixed.
    
12. If all is okay, this is where you wrap the wires. You can use either shrink wrap, or electrical tape. Shrink wrap looks more professional but cost more money. Electrical tape is nice and cheap and works just as good.
    
13. All done now re-install your new wire harness and your good to go.