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I've custom built at least three engine harnesses and maybe four versions of chassis harnesses for my car. Figured I could share my experience and have a thread that I can reference later on for parts.

For every wiring job, you'll going to need the essentials:

Stuff that will help you, but isn't absolutely essential:
- multimeter - ATD Tools 5536 Digital Multimeter: Automotive
I test continuity almost exclusively -- and having a multimeter with a buzzer helps quickly identify where wires are running.
- soldering iron / station -
Having a station makes soldering much much easer. A battery operated one is nice too, but they tend to lose their ability to heat up quickly.
- power supply station -
A power supply station lets you easily test sensors on a bench. Concerned an IAT sensor isn't working... turn on the power station, apply 5v, test the sensor.
- test leads w/ alligator clips -

Your best websites for wiring supplies:

For new Honda connectors and pins:

For circular, quick disconnect, mil-spec plugs: -- Good kits which will have everything you need for a first time build. -- Good for individual components -- Decent plugs, they are plastic and the locking mechanism is easier to use, but it's bulkier than the above kits.

In terms of building harnesses, it's all about planning. I use Excel to have a spreadsheet to quickly see where wires are going, and AI to provide a visual representation of what is happening. I do most of this first, so I am not sitting at a table staring at a ton of wires trying to figure out where everything goes. See attachments for those examples.

How to pin, wire, depin, rewire, concentric twist, heat shrink, etc... HP Academy is a great source for info:

I personally hate breaks in my wires ... If I need to lengthen or branch off a wire, I usually run a new wire from the connector and branch off from the terminal, if necessary -- instead of doing a quick tap. In some cases, that's just not possible (ie. fusebox wiring where you have grounds going to three different relays).

In my setup, I basically took out all of the wiring that manages engine control functions, including relays... and replaced it with a Honda based setup. So, I took my car's OEM ignition, constant 12v, ground, starter signal, tach, and coolant... then plugged that into my own custom Honda based setup.
I have my Main, Fuel, O2, and A/C relays wired like how Honda would.

Anyways, I hope this is somewhat helpful, if not for finding new connectors/pins.


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