Have you wired a car?

[jaybee]

Who has wired a car from parts as opposed to starting with a kit from Painless or one of the other vendors? Sure, the kits are great with clearly labeled wires, harnesses to different parts of the care pre-separated, and the fuse block already finished, but that isn't my question.

What's your experience/advice for this? I'm open to anything..."so simple even a cave man could do it", "wtf was I thinking?", "it was interesting and I know exactly how it's put together now", or "by the time I bought 50 colors of wire I could have paid for 3 kits."

It seems to me any car that's complex probably needs part of it wired differently or in addition to what's in the kit anyway, particularly if you get into things like EFI.

Thoughts, anyone?

[idrivejunk]

I have only done a little, and with factory style harnesses. I would say buying a package would be the most of what you need for the least of your time and cash.  However, if a guy had access to nice pricing on a few bulk items, it could also be done from scratch on the cheap but with more headaches. I was turned onto the "How to wire a street rod" book and that thing would be real helpful to a guy like me who just never grasped electronics. I mean I know how to torque down a plastic intake and can have my own fuel rail off in under five minutes, but I need lots of help when it comes to wiring. The pre-fab kits are so very nice, with the wires labeled all the way out and the fusebox in place.

[enjenjo]

I have wired a bunch of cars from scratch. The first one in 1964. Unless the car is a real oddball, or you are doing a cotton covered wire job, you will be hard pressed to beat the price of a kit. And wiring a car, and wiring EFI are two separate things. Normally there are only a couple wires from the car harness to the EFI harness.

By the time you buy 10 to 12 colors of GLX wire in two or three sizes you will have more than the price of a kit in wire alone, and you still need terminals, and in some cases special plugs at $3 to $4 each. Relays, fuse box, some way of mounting it, and you've added more. You can salvage plugs, relays, switches, and even wire from scrap cars, but if I am doing a customer car, that doesn't work., it's not cost effective.

Would I wire my own car from scratch? Yes, I have in the past, and I will do so in the future, but I have a substantial investment in tools and materials.

Now to EFI. If you can get an aftermarket harness with a PROM that will work on your car, or on later models, re-flash the computer, do it. Most aftermarket harnesses give you options on emission controls, and a fuel map that works better with modified engines. My current favorite is Howell Engine Development. They will talk you through any problems, and with the right info they can re-calibrate the computer to work on your application.

Besides doing them from scratch, I have used harnesses from Rebel Wire, Haywire, Kwikwire, It's A Snap, Francis, Painless, and EZwire. They all work, some are better than others, but none of them are bad.

The hardest color wire to find is tan for fuel pumps and gauges. I buy from both WayTek, and Del City wire, For cotton covered wire or armored wire, Rhode Island Wire.

A little trick, if I am running short on colors, I draw a tracer on the wire with a Sharpy. Black on most colors, Gold or silver on dark colors, and red or blue on light colors.

In wire you can get both light blue and green, and dark blue and green. WayTek colors are slightly different than Del City colors. Del City will do custom colors and tracers with a 500 ft. minimum.

[jaybee]

Good tips. There are also instructions out on the internet on how to remove wires you won't be using from the factory EFI harnesses. For example if you aren't using cat converters you only need one set of O2 sensors...but as you've noted the PCM needs to be reflashed to accommodate that.

Is there a standard for colors normally used for different circuits?

[enjenjo]

Is there a standard for colors normally used for different circuits?

Use any GM wiring diagram from the 70s or 80s for the color code. That is what most of the aftermarket harnesses use. GM was more consistent than Ford or Chrysler.

[purplepickup]

I'm about as far away from a car wiring person as you can get.  I have to think about it as plumbing with valves, shut offs, and such...and that analogy doesn't always work.  Anyway, I got a Painless kit and did the wiring on my pickup and haven't had a lick of problems since.  Well, I am having some issues with the cruise control and turn signal relay because I switched to LED lights but that doesn't count. I've been told they sell thingys to fix that.  My head just isn't geared to wire a car from spools of wire.  Yeah, for me, the kits take the guesswork out of it and make it do-able...a confidence builder too.  Heck, I even added a burglar alarm system and that wasn't even in the Painless instruction book.

[wayne petty]

stuff that is NOT always covered...

the main battery cables around the engine bay...


Positive battery cable to the starter..
positive cable to the power distribution block or underhood fuse relay block.
positive cable from the alternator to either the starter top terminal.. the battery terminal or the underhood fuse relay block or distribution terminal..

what.. positive to the starter is expected...

positive to someplace where the rest of the car can be powered..

positive to the alternator output terminal..

there are a whole bunch of ways to run the positive side..




the Negative side is slightly easier..

Negative battery terminal to the engine block.. usually to the block itself.. not a bracket..  or anything aluminum unless its an aluminum block and then to a double ended stud ..

negative battery terminal to the body.. usually the inner fender .. but it depends on the car.. the radiator core support is the other choice..  again depending on the car.. this is where the grounds for the front lighting come from..  this can supply the body of the car depending again on the car..

lastly the most important and overlooked connection on the negative side.. the back of the engine.. to the firewall..   and this is usually a braided ground strap as electrons like to flow on the surface of the wire strands..


again WHAT.. why...  when the engine is running and the alternator is charging.. the Negative voltage on the engine block from the alternator mounting is higher than it is from the battery..  electrons flow from the engine to the body in the shortest way possible..   this shortens the path..



and one additional thing..

if you run an external ignition module / box..  make sure the large ground cables are connected to the engine block/ heads/ intake..  

why.. the high voltage spark from the coil goes thru the spark plug wires and into the block.. how does it make a complete circle back to the ignition module/box from the engine block up the main battery cable to the core support thru the inner fender to the firewall. or some other lengthy path..

nascar racers have found that creating a triple ring terminal wiring harness..   one ring terminal on each head.. one on the distributor housing and the 4th on the firewall where the ignition box is grounded to the engine block with the braided cable also.. really really helps the life span of the ignition box.. shortens the return path of the high voltage spark thru the negative side..



you will want to print this .. and stick it to a wall.. perform the whole test or just the 4 part version of the test to verify that everything is properly attached..



just a few thoughts from the sidelines..


if you are going to run a disconnect switch.. there are 4 pole switches available now... you might want to run it this way..  with a warning.. if the switch is tripped off with the engine running.. there is a chance that it may blow the alternator diodes.

[jaybee]

Great stuff, this is all really nice. More thoughts on voltage drop --

Besides proper grounding voltage drop is a function of wire gauge and length. It's the reason why late models all have a second fuse and relay box somewhere at the front of the car, on or near the core support. That way the high draw headlights and electric fans get short wire runs through relays mounted in the distribution box.

For the same reason the voltage regulator wire of the alternator goes to the power distribution block. Voltage needs to be at spec where the power is used, not where it leaves the alternator. Seems to me that means adequate wire size and short runs become even more important on a one wire alternator.

I've also seen some sources that recommend running a ground wire from an electric fuel pump back to the engine block. The reason is that pumps don't tolerate voltage drop well and giving them the best grounding improves their longevity.

[kb426]

I've used factory harnesses for the brand of engine and associated components. I found a wiring diagram and removed all that was no longer needed. It wasn't as neat as a start from scratch good kit but I never had any trouble either. I like using factory parts if replacements are readily available. Being able to hit any parts store on the road has some comfort factor. The only other thing that I have noticed in the last ten years was the use of high temp crosslink wiring. I used that on the 32 where the under hood temps are about the same as the exhaust. That wire has been flawless so far. My normal use is 200 miles without stopping. The handle on the hood panel is so hot you can't touch it. The older wire would have had problems being under extreme heat for hours. There's some really good components out there if you want to piece meal it together. As long as a guy uses relays and good wire, I don't see a problem with this. There is surely a wiring diagram for most anything you want to do that is available with a search. In regards to grounds, the 96 Mustang I disassembled had grounds all over it. Most major components had a ground right next to them. I think a room full of engineers has more knowledge about this than me so from now on, I'm going nuts with system grounds.

[jaybee]

Good tip on the crosslinked polyethylene, the insulation has a much higher melting point than less expensive wire. I've noticed the same thing about late models...they have a multitude of grounds. The OEMs don't waste money on what they don't have to...so it's only possible to conclude it's a good idea.

[wayne petty]

these are the EXACT reason i use the printed voltage drop test above..

it took me a bunch of years to fine tune it..  i can perform it in under a minute on most cars..  

copper wire is expensive.. there are hundreds of feet of it in each car..

with the negative ground swap back in the early 50s.  electrons are now flooded into the entire body of the car..   this repels negative electrons found in the outdoors so less stuff sticks to the car..  sort of an early reversed electrostatic charge.  

if you charge something with positive voltage.. and the spray gun negative.. the paint goes right to the part without much over spray..


hint... if you want to make really nice wiring harness..

use something like clear vinyl hose and push fittings to duplicate the runs..  and the angles of the side outlets..   transfer that entire harness mockup to either a piece of plywood with drywall screws to keep the alignment.. or pegboard and tie wraps..  then you can duplicate it.. with wire.. tie wraps.. inch and a half wide electrical tape ..  zip tubing.. or.. if you can find somebody..  there are a hand full of companies that might still have a cotton overwrapping machine..   i saw one about 20 years ago i think in an egge machine catalog but i have not ask them about it..



oh... and investing in a set of these.. may save one HOURS and hours of work.. in harness termination..

http://www.allelectronics.com/make-a-store/item/ct-1/crimp-tool/1.html

this second one is for weatherpac terminals.. used on a LOT of devices..
a lot more money.. but still a needed tool..

http://www.allelectronics.com/make-a-store/item/ct-18/crimp-tool-for-weatherpack-connectors/1.html

[GPster]

I've used factory harnesses for the brand of engine and associated components. I found a wiring diagram and removed all that was no longer needed. It wasn't as neat as a start from scratch good kit but I never had any trouble either. I like using factory parts if replacements are readily available. Being able to hit any parts store on the road has some comfort factor.

This is the idea I had on the Jeepster.  With everything matching '87 GMC S15 (and the fact that I bought all the pieces together). I got pointed by Wayne to factory wiring diagrams and of the 30 pages I got them down to 9. The main problem is that I had originally was planning to keep the original Willys instrument panel and use mechanical gauges plumbed into the new/different engine but even though the 700 transmission is not computer controlled and has the standard cable type speedometer drive all of the engine's electronic data, the tachometer for engine speed and the vehicle's speed and transmission gear all send their information from the instrument panel to the computer. So I think the S15 panel is a necessity and the Willys' factory panel would just be an confusing duplication. Lets hope all goes as re-planned. GPster

[phat46]

I have also done it both ways. Buying a harness makes it simple, and fast. It only took a few hours to do my '46 Chevy with a kit, and it has provisions for  things like AC and power windows if I want that in the future. It's really plug and play. One the other hand I did not learn much about the electrical system using the kit. When I wired from scratch I learned a lot. I made mistakes and had to figure out what was wrong. I even had to take the steering column apart to figure out how to make the turn signals and brake lights function. I would say if you just want to get it wired and be done with it use a kit, if you want to understand the wiring better do it from scratch.

[jaybee]

It would never have occurred to me to run a mockup harness through the car but it's a good one.

I don't know if anyone still has contact with him but Skip who used to hang out here was cotton wrapping wire looms as part of his business. It was even written up in Street Rodder once.

We've been through this before on RRT and the general consensus is that most connections should be made with crimps made with a QUALITY tool as opposed to soldering, correct? I know that in my case getting a tool that makes good crimps made the process about 1,000% more reliable and easier too.

On a semi-related point it's well into the 21st Century and my toolbox still holds an analog VOM from Radio Shack. As a result I can't test a lot of things and chasing down electrical gremlins is often more difficult than it should be. Today is my birthday and I'm getting a Power Probe circuit tester that'll bring me up to date. Can't wait to get it, though I can wait to need it.

[enjenjo]

I've used factory harnesses for the brand of engine and associated components. I found a wiring diagram and removed all that was no longer needed. It wasn't as neat as a start from scratch good kit but I never had any trouble either. I like using factory parts if replacements are readily available. Being able to hit any parts store on the road has some comfort factor.

This is the idea I had on the Jeepster.  With everything matching '87 GMC S15 (and the fact that I bought all the pieces together). I got pointed by Wayne to factory wiring diagrams and of the 30 pages I got them down to 9. The main problem is that I had originally was planning to keep the original Willys instrument panel and use mechanical gauges plumbed into the new/different engine but even though the 700 transmission is not computer controlled and has the standard cable type speedometer drive all of the engine's electronic data, the tachometer for engine speed and the vehicle's speed and transmission gear all send their information from the instrument panel to the computer. So I think the S15 panel is a necessity and the Willys' factory panel would just be an confusing duplication. Lets hope all goes as re-planned. GPster

The only information the computer needs from the instruments is Vehicle speed. And there are several Vehicle speed sensors that will fit inline to the speedo cable that will provide the correct signal.