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I'm not done with my harness yet ( http://locostusa.com/forums/viewtopic.p ... &start=250 ), so I don't have a full opinion, but several times today (and before), I've considered the notion of making my own harness. I sure wouldn't change course at this point, but maybe for "next time."

I think a good way to go would be to open up the factory harness on the bench. Pull out the engine harness, ECU, and as little wire as needed to get those married. Install those parts.

Then cut out individual circuits from the harness (lights, ignition, diagnostic module, pedal switches, etc.) and transplant them one-by-one into the car, cut to fit.

I guess it would change the fundamental approach from "trim out what you don't need" to "carry over what you do need."


I'm sure it would have its own piles of frustrations, but in a lot of ways I think it would be easier. I dunno...what do you guys think?

-dave

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

I've considered that myself Dave. If I ever do an engine swap I might get a chance to try it.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

(moved this from my build log to the electrical forum -dave)

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

I would reccommend going through each harness (after removing the electrical tape and using some goo-off) and chopping out unused wires (power windows, ac stuff, audio, etc). This leaves what you need, but not at the correct lengths. I removed sections of the long wires and butt spliced the remaining parts together. You could also shorten the wires and re-pin the new end to fit into the connector.

Also, since a lot of the connectors have wires removed, you can consolidate the wires all into one connector (so long as the wire gauges are the same) by moving the pins from one to another.


Ideally, after chopping out unused wires, you would transfer what wires you need to the car, and then repin the wires into the appropriate connectors. This gives you the perfect length wires (w/o tons of splices), and no tangled wires. You could probably even get away with a one or two piece harness (main and rear).



besides the goo-off to un-sticky the wires, i would also recommend using tons of temporary zip-ties to keep certain bundles of wire bundled. This helps prevent the "oops i re-routed that wire through a bundle on accident" syndrome.

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Georgia Tech
Ride and Handling Engineer for a major car company
Locost finished - book frame, IRS, '84 celica GTS donor, '99 tacoma 2rz motor with a turbo, megasquirt DIYPNP. Getting rebuilt with new IRS, F20C
"the all-consuming time-sucking car, which I really enjoy working on" -KB

I like the little two-sided velcro cable-organizing ties for temporary organization. The type intending for taming your home stereo or computer. You can open and re-close them as often as needed.

I also used a lot of 4" wide stretch-wrap plastic. (Kinda like Saran wrap). Good for taming big, long bundles of wire. As a matter of fact, I use that stuff for *lots* of things...amazing how strong it is after 3-4 wraps. Particularly good at binding a camera tripod to things.

-dave

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

One way to go here is to get some pegboard (or maybe just some regular plywood and drill strategic holes) and start with string, or colored wire. You can make a mockup of the engine bay, all distances and splices correctly positioned on the board. Then, use that mockup to build your own harness.


I like pegboard and some dowel rods, personally.

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Old car restoration experts, help me out. I've got a 1977 Capri that will need some serious attention. Pics of the restoration project http://1977caprirestoration.shutterfly.com

I first tried to remove all the useless wires in the harness, tracing each wire back to the fuse box or switch, I removed each wire in the various multi pin plugs as I went. After about 15 to 20 hour and not even 'half way" there are a hell of a lot of wires in a modern car. I start fabing my home built harness. I did copy most of the factory color code for the basic items. I would say the most important thing is to actually draw up a harness schematic "you will needed it" I basically used the engine harness to the ECU, and just shorted the wires. The rest of the harness you can string out on the car and use tape or vel-cro to hold the wires in place as you add the various lite and switch wires. I would also suggest that you put in spare wires for added accessories in each of the three main bays. You would not foreget or need a wire after completing the harness [would you] !!!!! Another suggestion that I found helpful was to get plugs for trailer lite kits. Helps make water proof connections for your lites and fuel pump etc. etc
For the schematic I took copies for the factory schemtaic and enlarged them, then I did a paper dolly cut and paste along with a little white out. You will need a sheet about 30 x 20" so you can layout the lines and still have room to able to follow the wires on the sheet and add ID codes. The schematic will take a good 20 hours but will save you three times that when putting everything together. It was very helpful when you could only work on the car one day very week or two. Because there is know way you can remember all the color codes and routing. I would say that a race harness is going to take 30 to 40 hours and a full road car probably 70 to 80 hours to design and build.
I added another 20 hours because I solded all the connectors.

Good luck on the wiring you'll need it. Dave W

I looked at that route. But, considering that I don't have a "donor" per se (rather, a collection of stuff from a bunch of cars, mostly Ford...except for the steering column & rack), it would have been tough. Plus, a huge volume of stuff was dedicated to the ECU (no longer used), the fuel injection (not me - got Webers), dozens of sensors (do I really need to know what the torque converter temp at stall speed at a given RPM, altitude, throttle setting, etc. is? Uh....no.), etc. So....I'm going to go with an aftermarket hot rod harness, probably a 14-circuit or something like that. They're plug-n'-play into my steering column, everything is color-coded AND labeled every foot, come with the fuse panel (with all relays & fuses in place!), and use heavier-than-stock gauge wire. I've seen these on the 'net for as little as $150...I couldn't even buy the wire for that. And, not that my time is worth much, I don't have much of it either, so this is the simplest option.

Another consideration is that all of my '80's vehicles are starting to have problems in their original harnesses. I'm finding a series of failures inside otherwise perfect-appearing connectors, and the wires near them, in my Porsche 944 and Fiero GT. They are a REAL pain to track down, as even if you separate the connector, things look good inside...but they can be bad, or worse, intermittent. Given the extensive "modifications" a lot of builders are having to make to their harnesses anyway, trouble-shooting could be problematic, to say the least.

Just a thought....

Dave, I'm in the middle of constructing a harness from scratch. I started with a 1999 Miata schematic (donor engine for my D-Prepared solo car), a 2001 Miata schematic (for the ABS system), the schematic from my Haltech E8, and the schematic from my Stack dash. Add in a few extras for solo racing - and delete all the lights.

I ended up drawing up three separate schematics (ecu, dash, chassis & brakes) and then integrating them together. Actually, I drew up about 14 schematics, one for each subsystem, fuel pump, ABS, engine sensors, ignition, injection, launch control activation, roll control, charging and starting, auxiliary power, dash and it's sensors, and computer hookup for the dash and ECU. Then I worked them down to three major systems (ecu, dash, chassis). I worked it all the way down to one integrated schematic, but backed off back to three in case I decide to ditch the ABS because I can't get it to work, or in case I change out the dash.

At this point, adding headlights and running lights, turn signals, brake lights, reverse lights, wipers, and illuminated gauges and hi-beam indicator would be easy.

It was easy doing this in Viseo using their Electrical Engineering clipart. But I had to figure out the amp draw on my own. The wire size and circuit breaker depend on the amp draw.

I'll be glad to send you a copy of my files Dave. I may be able to export them to some generic file type.

I think I'm past where they'd be useful to me, but I wouldn't mind looking at them all the same. I'll see if anyone at work's got a copy of Visio. If it exports to a CAD format, I can use that.

Thanks, Beat.

-dave

_________________
...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

I've got Visio, CAD and acrobat. If you send them to me, I can post them in DXF and PDF.

William

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William Conway
Building the Spartan 7 - Build Blog
LocostUSA Build Log
How do you eat an elephant? One bite at a time...

I have a lot of professional experience with big wiring mods.

A few rules of thumb:

Wiring should be done last, after everything is exactly where it needs to be.

Make your slices on one end anytime, but don't do both ends until the wiring bundle is tight all the way to the other end.

Leave slack at the ends between a part and a frame clamp.

Try not to have all the splices in the same spot. Stagger them.

Don't splice within a foot of the connector.

Solder the connections in the manner shown in the doodle.

Your doodle looks like a poor man's version of what they want solder jobs to look like on aerospace/mil spec stuff. If they are stranded wires, flow solder onto both ends. Lay them next to each other and wrap some thin copper wire around the bundle. Then add solder and clip the end of each wire at a diagonal (this step minimizes sharp edges that can pierce the heatshrink).

Thanks!

The ends of the wire in my doodle can be clipped as easily as when using a third wire. I didn't think I had to explain everything.

I have more than 30 years in electronics. The double twisted joint is how "they" want things to be done. For my personal stuff, I just cut the wires, strip about 3/8 inch off each end. Slide a piece of heat shrink about 3/4 inch long over one end and sllide it away from the joint. Lay the 2 wires side by side and solder them. No extra wrapping- nada. Slide the heat shrink centered over the soldered joint and apply heat, usually a match or a butane lighter. I have never had a joint fail. This should be good up to #18 gauge wire, a little smaller than the size of a round toothpick.

This joint will be stiffer then the rest of the wires and will not bend

Sometimes I will fray the ends of the wire and push them together before soldering. Sometimes I will add a 2nd, larger piece of heat shrink depending on the application.