Rewiring my project and how you did it

[Dodgefran]

I am starting from scratch on my project in a few weeks.  The previous owner stripped the wires completely so I have only a diagram to follow.  Wire rolls from the parts store, Rhode Island Wiring, or one of those wiring harness kits on Ebay?  I was wondering what and how some of you have done it, and some sage advise on what you found doing the job.  Thanks in advanced.

 

Dodgefran

[Restorer32]

What car?

[Dandy Dave]

I've built a complete wiring harness from scratch on vehicles that are rare and replacement harnesses are not readily available. Something like a Model A or T Ford just buy the harness already made. Agree with Restorer 32. What Car?  

[Stooge]

I like wiring, i've done a few cars from scratch both in stock and custom forms, and its very satisfying if you take your time and have a good plan, and real frustrating if you try and rush through it. As far as non specific vehicle advise, get a pen and notebook, lay the harnesses and wiring you have out on the floor and slowly and leisurely, start making sense of what needs to route where, whats doing what, and start setting it out on the floor how it will be routed in the car. Leave everything a little long, especially under dash/ hard to reach things that will save you aggravation when you have to take a gauge cluster, light, etc out and you have enough wire slack to access something. Get some decent snips and crimping pliers that you wont be cursing at every time you use them. I even painted the underside of the last dash white while i was painting, so when i got to wiring that truck, it made it alot easier to see under the dash rather than being black or something and needing a flashlight for everything. 

Edited May 25, 2021 by Stooge (see edit history)

[ojh]

Really need to know what car and era you are working with, how original and the voltage, like if you had '40's era car and are changing it to 12v, that'll make quite a difference on materials and technique.

[zeke01]

It has been many years, but when I rewired my 1948 Jeepster I used an assembled harness. I closed the garage door and dared anyone to bother me or try to "help" me while I was working. It worked. Zeke

[28 Chrysler]

I have rewired from scratch and also have used Rhode Island Wiring. The folks at R.I. were great as well as their  harnesses.

[Str8-8-Dave]

I'm gonna hazard a guess based on Dodgefran's recent posts that the subject vehicle for rewire is a 1938 Dodge truck.  If it is and someone other than him removed the original wiring he will face some of the same challenges I did described below and may not have the luxury of factory electrical layout drawings that really helped me overcome the same situation of not having the original wiring to remove and copy routing from.

 

I think one of the greatest challenges to rewiring from scratch is harness routing.  I bought a reproduction harness for my 31 Buick project from Harnesses Unlimited.  The first thing in the installation instructions is to carefully remove the original wire harness noting how it is routed and set it aside for reference.  The previous restorer had already removed and discarded all except the rear body tail light harness for my car.   I was lucky enough to get Buick electrical drawings which laid out routing pretty clearly by showing the wire harness attachment points to various components of the car including side frame and cross members and firewall layout.  All electrical hardware such as the headlamp switch, horn, ignition switch and current limit relay were shown with terminal by terminal connections and factory wire colors shown.  Shoulda been a piece of cake right?  It probably would have been except the Harnesses Unlimited wire harness DID NOT follow the factory wire colors and was a wire by number project without any diagrams to show end point connections to components or component to component wiring.  I had to sort a lot of that out but patience paid off.  I had no issues when the battery was finally wired in, no smoke and everything worked correctly.   

 

One of several Buick electrical drawings I got from Chuck Hoffman, contains end-to-end connections and wire color codes as well as physical routing information.  These were a luxury since the previous owner removed the original harnesses, I started from scratch.

 

The Buick  current limit relay was the central point of the new wiring harness installation, think of it as the fuse box or load center.  

 

I bought a complete reproduction wire harness from Harnesses Unlimited.  Assembly quality and directions were excellent but oddly it was not faithful to Buick production wire harness color coding, instead it is install by number.

 

The current limit relay mounts on the firewall inside the insulator pad and left and right engine compartment harnesses pass thru the pad and are clipped in relief channels in the firewall so the insulator pad attaches flat to the firewall sheet metal.

 

A view of the firewall channels which are shown on the Buick drawings

 

Right side harness goes to generator cutout relay, ignition coil and gets the accessory feed from the starter terminal.

 

You can see in this picture how the left side harness enters the engine compartment.  It clips to the frame on it's way to the headlight switch.

 

The headlight switch distributes power fed from the current limit relay forward to the headlights, up to the cowl lamps and rearward to the stop light switch on the frame under the drivers seat floor.  Power for the dome lamp comes from the headlight switch as well and the horn wire comes out of a steering column tube in the center of the switch. 

 

The headlight harness crosses from the left engine compartment across the cross member just behind the radiator.  Having the radiator out of the car to make repairs to the shutter and thermostat mechanisms made this routing job a little easier.

 

This is a view under the dash of the instrument panel wiring hookup.

 

 

Edited May 27, 2021 by Str8-8-Dave
Add pictures, descriptions (see edit history)

[kingrudy]

I did my 1940 Buick with the complete harness, two sections from front to back from YnZ in California. Great instructions and very knowledgeable people when I called with a couple of questions. 

[JACK M]

I have done several and with all of the methods mentioned.

I am lucky that I have a general knowledge of how things should flow electrically.

The first car I wired from scratch I used wire from old outboard motor  harnesses as the wire was free. That car is still driving after 40 or more years.

I kind of like these new aftermarket harnesses as they print what each wire is for every couple of feet.

Best advice is don't be in a hurry.

Don't be discouraged when you are at this stage.

Edited May 25, 2021 by JACK M (see edit history)

[1932 plymouth pb sedan]

It really depends on what YOU want. Save a little cash?, wire it yourself. Do you have all the proper wiring connectors?, will have to order them and wait. Do you want period correct reproduction and exact fit?, Rhode Island Wiring builds that and in a reasonable time frame. Ebay ?, most likely made in China and not even close to what you were expecting. Please post updates and pictures.

[Dodgefran]

Thanks for all of the answers.  There seem to be quite a few choices for sure.  That's what I like about this forum.  Years ago when I joined, there were some "participants" who would have (and did) answered "Why do you want to do it that way for" instead of telling us How they did it.  There are as many ways to do something.  We try it and if it works, we pass it on.  If it doesn't work, we "change the subject" <:-).   Your different choices are the underlying info that I need.  I'm relatively new at this at 79.  Keep the info coming for guys like me.   Thank you, Thank you, Thank you,

[Bloo]

I have built plenty of harnesses in my life, but if this is a very old car, and stock, and if the harness is available from Rhode Island Wire or Ynz, I would do it. There is something wonderful about parts that just fit. If you want to roll your own, those two companies, as well as Brillman Co., have cloth wire and many of the other supplies you might need. Making a whole harness for a car and making it fit right is a whole bunch of planning and work, more than it seems like, and that makes off-the-shelf whole harnesses look really attractive to me.

 

If it is a car new enough to have plastic wire, I am not sure who to go to for a whole harness, but it would still be my first choice if available. When building a harness with plastic wire, getting decent wire is always the problem. The stuff available at the parts stores feels cheap, the strands are too big for best reliability, and it is really expensive. Stranded house wire (thhn or mtw) is a possibility too, but it is pretty stiff and not at all friendly to work with. Split loom is atrocious crap that takes up way more space than it should and looks bad. I wont use it unless the car is modern and there is a bunch of it already in place that is going to stay. The non-adhesive tape used on older cars can probably be found today, but is really horrible stuff to work with, very difficult to make it look good. I have come up with my own methods using regular electrical tape that don't wind up as a sticky mess and are difficult to distinguish from factory work. It is still a lot of work and I would never do it these days if a nice off-the-shelf replacement harness is available.

 

Then there are kits from Painless Wiring and several others that are a fusebox with a bunch of plastic wires attached. Due to the market they cater to, they have to be usable by your Grandmother, your dog, and anyone else with limited mechanical or electrical experience. You still have to bundle the wires up for a nice fit on your own just like you were making the harness from scratch. Since they are universal, you also wind up with splices in places that i would NEVER put them if I were making a harness. They expect you to crimp the splices. Crimping will degrade over time, and the splices will probably be buried in the harness. I am not going to rule these harnesses out completely and say I will never use one again, but I probably won't. For most cars there will be some better way. Also, they are only useful if you are building a 12 volt system.

 

 

Edited May 27, 2021 by Bloo (see edit history)

[hchris]

Ok here's my pitch, doing a 34 Chrysler some years back I had a wiring diagram to follow and used an old hot rodders guide.  Went to the local hardware store and bought a couple of reels of cheap plastic/nylon clothes hanging line; with the aid of wiring diagram ran and cut each wire in nylon, labelled them as I went then laid them out on the floor. Zip tied the lot together and ran the loom through the car snipping/ adding where required, once happy with the fit replicated the whole thing with proper cable and fittings and installed, also this gave me the flexibility to add/alter stuff as I went, such as turn indicators etc.

 

So whilst doing the job twice it worked out pretty cheap, as I was able to sort my mistakes out before making up the real deal, and have to say enjoyed the project along the way 

[Stooge]

7 hours ago, Bloo said:

I have built plenty of harnesses in my life, but if this is a very old car, and stock, and if the harness is available from Rhode Island Wire or Ynz, I would do it. There is something wonderful about parts that just fit. If you want to roll your own, those two companies, as well as Brillman Co., have cloth wire and many of the other supplies you might need. Making a whole harness for a car and making it fit right is a whole bunch of planning and work, more than it seems like, and that makes off-the-shelf whole harnesses look really attractive to me.

 

 

 

I misread or missed part of the original post and thought the original poster already had the materials to do a scratch built one, or harnesses to piece meal it together. Rereading it, and what i would do myself if it is available, would definitely to buy a complete harness and install it.  The time saved of having something that 'just fits' is worth whatever savings there would be making your own, sourcing terminals, etc. 

Assuming, they are working on a 1938 Dodge 1/2 ton from their other posts, a little over $400 for the main engine, dash and body harness, and $100 for the headlight harness from Rhode Island wire would be money well spent in my opinion 

Edited May 27, 2021 by Stooge (see edit history)

[Pilgrim65]

Still would have been nice to know the project , makes it worth while 

[Dandy Dave]

12 hours ago, Dodgefran said:

Thanks for all of the answers.  There seem to be quite a few choices for sure.  That's what I like about this forum.  Years ago when I joined, there were some "participants" who would have (and did) answered "Why do you want to do it that way for" instead of telling us How they did it.  There are as many ways to do something.  We try it and if it works, we pass it on.  If it doesn't work, we "change the subject" <:-).   Your different choices are the underlying info that I need.  I'm relatively new at this at 79.  Keep the info coming for guys like me.   Thank you, Thank you, Thank you,

So Dodgefran. What are you rewiring? Dandy Dave!

[Akstraw]

I really enjoyed making a harness from scratch, although I have used RIW harness as well.  As a retired engineer, I liked the planning, layout, list of materials creation, checking, double checking, etc.  if those things don’t turn you on, then get the harness.  Do you have a basic understanding of electricity?  Comfortable with a multimeter?  Then you can do it yourself.  My motto:  “Electricity doesn’t lie.”  The meter will always tell you what is going on.  If you are doing it yourself, and want to be true to the original, shop around on eBay for partial rolls and odd lengths of fabric insulated wire.  You can do better than the per-foot price that many sources charge.  If you aren’t really particular about authentic insulation, then there are many sources.  Pay close attention to the correct gauge: 6 volt requires different from 12volt.  Just some thoughts.  And I agree with many of the comments above.  Good luck, whichever way you go.

[JamesR]

I would suggest that there can be a direct relationship between cost and convenience. I got a complete universal kit from a reputable wiring company that cost under $300 a few years ago. I had also priced out an exact replica of what was originally in my car several years before that, and it was $800 at that time...probably well over $1000 now. If you don't care much about originality, you may think that was a no-brainer, but the original replica wiring kit probably required less thought work during installation than the universal kit, because the original should drop right into the car...more or less the way other replacements part would. The universal kit is meant for a wide range of vehicles and must be adapted to the specific application. So I approached my installation by keeping the old wiring in the car and pulling it out bit by bit and only as it was replaced by the new wiring. This helped me figure out how I needed to adapt the new kit, but took longer. I also needed to figure out how to interface the new wiring with unique systems in my car, like turn signals.

 

It's not rocket science, but (as others have said) it's easy to screw up if you feel like you have to do it in a hurry (a few days or a week.) Always scrutinize the work you've done and I would suggest that you test each subsystem as you complete it, if possible (headlights, radio, etc.) Whatever you do, don't listen to the people who say, "It should only take you this long to complete the job." That will undermine your efforts rather than help them. I took a long time to complete mine and it turned out fine, even though I hadn't done it before.

[Dodgefran]

I'm sorry I haven't listed my "ride" guys.  Str8-8-Dave is right.  It's a 1938 Dodge Humpback Panel RC 1/2 ton.  I am stoked at all the choices and advice.  Without your help, I'd be reinventing the wheel again.  Thanks.   Keep the ideas coming.