Making your own wiring harness

[abecx]

I've completely pulled the interior in my RX7 and started unmounting the stock wiring harness. I intend to replace it with my own so I can get rid of all the extra connectors that I don't need anymore and also clean up the wiring mess making it easier to maintain. The stock harness in the car leaves much to be desired, some areas dont have relay's resulting in weak power windows and power spikes because of power drops. I plan on doing everything best practice since there isnt that much stuff I have to plug up.

The engine management is handled by a Holley HP ECU, it already has its wiring harness installed so I dont have to worry about that part.

I am trying to create a list of items I'll need to wire in order for everything to work as intended. I've done wiring, soldering and repairing of electronics before and understand how to not set things on fire, but I've never tried rewiring an entire car. Any input is appreciated.

I've broke down the wiring into 3 separate sections of importance. Primary items are things required for the car to run, secondary required for me to drive the car, and third is comfort items. Do you see anything I'm missing. Again, any input or links would be awesome.

Primary Systems:
  Fuel System
  ECU
  Alternator
  Grounds
  Radiator Fans
  Dashboard
    
Secondary Systems:
  Window Motors
  Head Lights
  Tail Lights
  Turn Signals
  Horn

Tertiary Systems:
  Nitrous components
  Air Conditioning
  Inside lighting
  Stereo
  Amplifier
  Speakers
  Door Locks
  Keyless entry

[LS1Goat]

Save yourself a lot of headache and just call Painless Performance and see what they have available. http://www.painlessperformance.com/

[Craizie]

Yes. Painless for sure. We used to have a member that worked there. Fitzwell maybe? Not sure what he currently does.

[BLAKE]

Fitzwell doesn't work there anymore, but I'm sure he would agree that it's a good start. He and I wired my '66 with a generic harness from Painless and I have nothing but good things to say about the materials.

Edit: I don't have it in front of me at the moment, but I think this is the one I used:

https://www.summitracing.com/parts/prf-10202

[JV106]

I used an American autowire kit for my fox. The kit was easy as that job could get but there were plenty of times during the install that I wished I would’ve just left the original wiring in it. Rewiring a car is a horrible job.

I bought a set of Astro ratcheting crimpers on Amazon. The one with 4 or 5 different sets of dies. You’ll want something similar for this task. GM weatherpack connectors are good too. Even with a kit you’ll probably want some type of connectors on hand.

[kingjason]

I used an American autowire kit for my fox. The kit was easy as that job could get but there were plenty of times during the install that I wished I would’ve just left the original wiring in it. Rewiring a car is a horrible job.

I bought a set of Astro ratcheting crimpers on Amazon. The one with 4 or 5 different sets of dies. You’ll want something similar for this task. GM weatherpack connectors are good too. Even with a kit you’ll probably want some type of connectors on hand.

I have had a set of these for 28 years. You absolutely can not pull the wire out of the connector after using them. Although, I did make the mistake of buying harbor freight connectors one time. Worst crap ever and would never hold a crimp.

[abecx]

I guess to clarify, I'm using the stock connectors I'm just splicing in new wires everywhere so I can tuck the cables, eliminate unused cable, and implement best practice to get rid of power drops. I dont need an entirely new harness.

I appreciate the feedback to buy one, but I want to make my own as a challenge to myself.

[svauto-erotic855]

but I want to make my own as a challenge to myself.

Big mistake and you will regret it. Just having the wire to build harnesses on hand cost me more than 5k. I bet I also have that much in crimping tools not to mention connectors and relays. Buy something off the shelf and adapt it to your needs.

[Gasser64]

I got to agree with the others here. Reading your past posts/threads, you're a DIY'er like most of us here so I can see why you'd wanna do this. But automotive wiring is the bane of many an existence. Guys that are great with cars often hate this. 1 mistake, one little fuck up, and you WILL chase your tail for 3 months. Only to find out it was the dumbest shit in the world. You'll think the problem must be this, no it must be that, no it must be the harness but the harness seems good, on and on.

So count this post as another 'don't do it, buy it somewhere' post. Although I'm not exactly sure where you'd buy that lol. Seems like it might be kind of a pain to find a new one, but what the hell do I know. Painless wiring seems to mainly deal in american stuff.

[Broncojohnny]

I guess I would have to see this in person to judge but just hearing few details this seems like a whole lot of work for very little return.

[garycrist]

Tough

As the others have said, it is a difficult job at best.
The different spools of wire it would take, will bankrupt
you in no time. If you have never had to trouble shoot
a bundle of mono color wires you do not know what you
are missing.

Salvaging a loom and adapting with aftermarket weather
resisting connectors would be a must! Forget crimps and
those worthless colored connectors unless you solder them too.

Document everything and draw a schematic of what you did too.

GL

I did wiring and electrics on all of the Italian makes in a prior life.

[Fatass]

I do the shit for a living and have to agree, it can be a motherfucker. But if your still up for it, I'd start by buying a good label maker and start making a wire list of what runs where, make drawings of the connectors and ID each wire on each connector diagram. Then start deleting the specific wires/connectors. Then I'd start extending what's left and solder every connection. Fuck crimping connections unless it's at a power source or ground location.

[abecx]

So far I've bought a label maker, relays, relay/fuse box, a shit load of varying cable ( 8-18 gauge ), some bridges, heat shrink, a ton of connectors, a butane solder, a nice side of crimpers and wire strippers. I'm going to be reusing some of the cable thats already there ( rear lights mainly ), and will be running new stuff up front reusing the factory connections for the headlights. The Computer is all using its own separate shit so there isnt anything I have to do there.

My minds already made up, I'm going to tackle this. I really dont think it'll be that bad just time consuming. I've already wrote out a diagram for where the wires are going to be routed.

[Fatass]

You'll be fine, you are correct about the time consuming part but it sounds like you've thought it out well enough that you more than likely won't have any trouble shooting to do. Document everything and take pictures for future use is about the only other thing I'd recommend in case you want to make a change later.

So far I've bought a label maker, relays, relay/fuse box, a shit load of varying cable ( 8-18 gauge ), some bridges, heat shrink, a ton of connectors, a butane solder, a nice side of crimpers and wire strippers. I'm going to be reusing some of the cable thats already there ( rear lights mainly ), and will be running new stuff up front reusing the factory connections for the headlights. The Computer is all using its own separate shit so there isnt anything I have to do there.

My minds already made up, I'm going to tackle this. I really dont think it'll be that bad just time consuming. I've already wrote out a diagram for where the wires are going to be routed.

[Craizie]

You still have the pop up head lights?