Anybody built their own harness?

[Crusty69]

My 69 has a handful of electrical gremlins and being a 56 year old truck, it’s been messed with by who knows how many people over that span given it’s had an engine swap among other things. I think it’s time to just rewire the whole truck.

I know American autowire seems to be the way to go but a friend suggested building my own harness. I’m sure after factoring my time, it’s not worth it, but has anybody done it before? Curious to see what others have done.

[71meangreenc10]

If you have the access to all the connectors and correct wiring it is not that hard to make. Can you make a correct wire connection? The problem is if you do not, you are throwing money in the trash. The engine harness is very simple in circuits to build. The dash harness, a little more complicated.

Why do I post this. I own a 70 G20 Van. AA and other Wiring Companies will not touch my Van with a 10ft pole for a Factory Harness. How do I know this? I reached out to several to make a simple six circuit engine harness, and I had my original which could have been a good prototype. Over a year later, I am still waiting for a return call/email from one of those BIG companies. Just to be honest, one company did contact me and we had good discussion. At the end of the day, they said it was not financially good for them to make a new harness for my application. I think the Van community would have loved to have more options than just a generic Painless Kit.

So I made my own, I used Packard connectors, ordered the tools, ordered the correct wiring thickness with the correct colors and built my own. I did decide to change it, because I couldn't find the correct bulkhead connector and I didn't like GM's way of doing this. I am confident in my harness and I trust that it will not fail me and cause a potential fire.

AA makes good stuff and I use them for all my builds. Redoing the whole truck is going to be a big cost. If you are not doing anything special or adding more circuits to the truck, stock is fine.

Smitty

[Crusty69]

Originally Posted by 71meangreenc10

If you have the access to all the connectors and correct wiring it is not that hard to make. Can you make a correct wire connection? The problem is if you do not, you are throwing money in the trash. The engine harness is very simple in circuits to build. The dash harness, a little more complicated.

Why do I post this. I own a 70 G20 Van. AA and other Wiring Companies will not touch my Van with a 10ft pole for a Factory Harness. How do I know this? I reached out to several to make a simple six circuit engine harness, and I had my original which could have been a good prototype. Over a year later, I am still waiting for a return call/email from one of those BIG companies. Just to be honest, one company did contact me and we had good discussion. At the end of the day, they said it was not financially good for them to make a new harness for my application. I think the Van community would have loved to have more options than just a generic Painless Kit.

So I made my own, I used Packard connectors, ordered the tools, ordered the correct wiring thickness with the correct colors and built my own. I did decide to change it, because I couldn't find the correct bulkhead connector and I didn't like GM's way of doing this. I am confident in my harness and I trust that it will not fail me and cause a potential fire.

AA makes good stuff and I use them for all my builds. Redoing the whole truck is going to be a big cost. If you are not doing anything special or adding more circuits to the truck, stock is fine.

Smitty

Good info. I’m running a couple extra circuits, probably a fuel pump, air conditioner, and stereo. Other than that I think it’ll be pretty straight forward. I’m back and forth on efi but the carb is just so simple. TKX is going in soon but I believe it won’t need anything.

[PbFut]

I will share there is one connector no longer available. It is the packard connector at the fire wall for the 4 wire ribbon that goes to the rear of the truck. The connector used on the interior harness used to plug into that 4 wire ribbon is no longer produced and American Auto Wire informed me they had bought the last run of them years ago. They will not sell this odd shaped 4 wire connector individually, AAW uses their remaining stock in their harness. They were polite about this circumstance and actually have a name for the status of parts in similar situations, though I don't recall what it is at the moment. I was able to obtain a used connector from a fellow board member. I actually had a couple responses to my request so they are readily available used. Also, the ribbon wire firewall to rear harness is not produced in the same color shades as the original. Close, but not exact for those looking at a perfect restoration. I found most everything else on the AAW engine, headlight, aux. battery, and interior AC harnesses to be very accurate with correct color, length and connectors. They even include that odd ball single connector tan wire at the engine side of the fire wall on my 72 harness. (not the brake warning wire). They also have options for HEI and internal or external regulated alternators so you can select the correct setup for your equipment options.

[Getter-Done]

A kit like this would save you half the work.
If this is the route you would choose most of the ground work is already there.

Coach Controls, Inc. has a few harness made up with relays incorporated in. They are a small (Made in the USA) shop in Cleveland, TN


Link: https://coachcontrols.com/index.php?...products_id=85

[HO455]

Another option would be to do what I've done on mine. I bought a new under dash harness and then built the engine harness.

You can try making a new rear (taillights) harness to start as it's simple and then you can decide if harness building is for you without diving directly into the under-dash harness. If you like it then build the engine harness to hone your skills before building a dash harness.

[MARKDTN]

I've built small harnesses. I've integrated stuff into factory harnesses. I have used Painless and some junky overseas universal harnesses. It's doable. But unless you have way too much time to kill and can get the right connectors and the tools to crimp them, you are better off on a stock truck to buy an AA harness if you want to customize. For a highly modified truck it may make more sense to make from scratch.

If you make your own, the hardest things to get right are the column connection and the dash connection. Small lamps are also not that easy. Sure you could crimp on a pigtail, but there is another resistance point added.

If you have no patience with wiring and have a basically stock truck, you are better off just buying full harnesses from M&H or Lectric Limited and just plug and play. They can do HEI and internal reg alternator if you are so inclined. Spend your time enjoying the truck rather than making a harness.

[MikeB]

Whatever you decide on, use cross-linked wire--TXL, GXL, SXL-- because it has higher heat and abrasion resistance than auto parts store wire. Here's a description from the Google AI:

TXL, GXL, and SXL are common automotive cross-linked wires, differing mainly in insulation thickness for specific uses: TXL (extra-thin) is lightest/smallest for tight spaces; GXL (thin) offers a balance of space & protection; SXL (standard) has the thickest insulation for maximum heat/abrasion resistance, ideal for engine bays. All offer superior heat/moisture resistance (e.g., -40°C to 125°C) over standard PVC wires, making them perfect for demanding vehicle applications.

Also, I'd say you must have a good understanding of automotive electrical circuits, because even experienced guys run into problems. Over the years I've installed four harnesses (all kits), and finished up a 5th that had not been completed. Have also redone the wiring on two engine compartments. Each installation had its challenges, even though I worked as an electronics technician for several years!

Edit: Although I've installed two universal kits, I much prefer a kit that's designed specifically for 67-72 Chevy trucks. I like American Autowire a lot. Excellent instructions and great tech support.

[A1971Blazer]

For me, time is the most expensive thing. The time spent building a harness from scratch would not offset the cost of buying one already made.
I can make more money, but I cannot make more time.
I used an M&H upgrade harness on my '67 build and did some custom modifications to suit my purpose. It worked out really well.

[MikeB]

Originally Posted by A1971Blazer

For me, time is the most expensive thing. The time spent building a harness from scratch would not offset the cost of buying one already made.

Even though I have the time, I can't even imagine buying all the wiring and sourcing the proper connectors and terminals. But I'm sure it's been done, replacing one wire or group of wires at a time. I bought a 55 Chevy car years ago, where shiny new wiring had been spliced into the original instrument panel wires, which was sort of defeating the purpose. New wire using 50-year old terminals and connectors!

One thing I forgot to mention in my earlier post: I suggest using one-gauge larger wire than what GM used. IMO, they always used the smallest gauge wire that would handle the current to reduce costs and save weight. Probably the most important is the charging system--battery to alternator--which was 12 gauge from the factory. On my 69 C10, I used 8 gauge to the alternator and 10 gauge to the fuse panel. Also, I can't remember the gauge size, but headlight brightness will benefit from larger gauge wire than stock.

[Orange Crate]

i chose to install a full AAW kit on my K20 build and then I built my own harness for the fuel injection. All the cautions stated above are a real concern, like the correct connectors and wire type. It took a while to get the parts together just for the FI (which is a relatively short engine compartment harness).

[LS short box]

On my 68 C10 with a LS swap I used a Painless 21 circuit universal chassis/dash harness. I saved all the old connectors off the old harness to reuse if needed. Painless uses the upgraded wire shown above and the wires are labeled full length. I'm sure AAW does as well.
The harness for the LS came from Howell as well as the ECM. Base tune in the ECM according to your LS combo.

[Sheepdip]

Nice part about purchasing a pre-made harness is all the wires about every 18" or so are labeled as to what they are for....makes it smoother and easier to separate/route everything properly.

[MikeB]

Originally Posted by LS short box

On my 68 C10 with a LS swap I used a Painless 21 circuit universal chassis/dash harness. I saved all the old connectors off the old harness to reuse if needed. Painless uses the upgraded wire shown above and the wires are labeled full length. I'm sure AAW does as well.

Did the Painless universal harness also use GM color codes and various GM-type connectors, etc.? That's the way it is with AAW universal kits, and an EZ Wire harness I used once. I feel for the Ford and Mopar guys.

It's still lots of work though. On the Square body truck I wired using an AAW Universal kit, the biggest pains were the instrument panel and windshield wiper/washer wiring. Had to buy a few connector blocks for those connections. Also the wires for rear lighting weren't long enough, even on a short bed truck.

The AAW fuse panel in the Universal kits is not made to fit any specific vehicle, but it is a very nice piece. Below is a photo the fuse panel on the Square body I mentioned above. I think that's an 8ga wire to the stud, and then 10ga to the fuse panel BAT bus and IGN switch. But it's been a while! Results were awesome -- much brighter headlights and dash lights, more voltage to the HEI, and even a louder horn!

FYI, I mentioned using 8ga wire a couple times in this thread. It doesn't come with any kits I've used, but you can get it from Internet vendors, like Jeg's. https://www.jegs.com/i/JEGS/555/10841/10002/-1 Seems like I found a better deal on Amazon or eBay.

[LS short box]

On my 68 with the LS swap I didn't use the stock fuse block hole. I patched it up and made a new hole with a grommet behind the the inner wheel well. There is not that many wires that run forward and back for the chassis.
I moved the Painless fuse block back a bit with a couple angle brackets fastened it to the side panel near the vent door.
In regards to wire length I don't recall having any issues length wise. GM wire color really didn't matter to me. You could check against a stock wiring diagram.
I love hiding wires.
Couple of pics.

[Steeveedee]

Originally Posted by LS short box

On my 68 with the LS swap I didn't use the stock fuse block hole. I patched it up and made a new hole with a grommet behind the the inner wheel well. There is not that many wires that run forward and back for the chassis.
I moved the Painless fuse block back a bit with a couple angle brackets fastened it to the side panel near the vent door.
In regards to wire length I don't recall having any issues length wise. GM wire color really didn't matter to me. You could check against a stock wiring diagram.
I love hiding wires.
Couple of pics.

I like that, as a nice clean uncluttered under hood. I'm too old and arthritic to tackle a job like that. Yours looks 100 times better than mine under the hood.

[LS short box]

Thanks for the kind words.
It was my first project after I retired a few years ago. Total frame off resto nut bolt rebuild.
When you think about wiring challenges a couple of pics before and after of my 67 Nova project I took on a number of years ago. Failed project I was able buy from the owner that got totally hosed by a somewhat local LS swap expert.

[tim_mc]

Wow - nice job LS short box! I used the AAW Classic Update kit in my '67 since I was going to make some common upgrades. Given its age, there wasn't any part of the OE harness I was going to use. Some points AAW makes about it:

* Longer length wire allows for stock or custom routing
* ATO-style fuse panel and more circuits
* Full color schematics and instructions
* Ignition, headlight, and dimmer switches (most kits)
* Upgraded 8-gauge wire for alternator, fuse link protection, gauge cluster options, and disconnect
* Pre-wired fuse panel mounts in the stock location

[tim_mc]

I just looked at the latest prices for wire harnesses. Ouch!

[pjmoreland]

I recently got a truck back on the road after it had sat for over 20 years with its windshield removed. The original dash, engine and headlight harnesses were hacked up beyond recognition and the fuse panel terminals were badly corroded. I scrounged around and found good used original replacement harnesses that were mostly complete for not much money compared to new. I made a few modifications to these harnesses such as increasing the size of the battery charging wire to support a high amperage internally regulated alternator, but for the most part they are still in stock configuration.

If I had started with harnesses that were not corroded and mostly intact with a few gremlins, I would have just taken the time to clean them up and return any PO "repairs" back to stock.

[MikeB]

Originally Posted by LS short box

On my 68 with the LS swap I didn't use the stock fuse block hole. I patched it up and made a new hole with a grommet behind the the inner wheel well. There is not that many wires that run forward and back for the chassis.

Very nice work. I'm more of a "form follows function" guy, which actually means I don't have the patience to do what you did!

Can you show us a photo of where the grommet is "behind the inner wheel well". Also a photo of where you mounted the fuse panel?

My 69: Fairly neat wiring, but not hidden.

[LS short box]

Sorry no close up pics of the grommet or fuse block mounting. I have since sold the truck to finance another project.
Couple more things I like to do wiring wise.
1. I will not use those cheap red/yellow butt connectors or male/female spade connectors.
I go to Fleet Farm or Fastenal and get the connectors that are the waterproof heat shrink type that have some type of "goo" inside that melts as you heat shrink the connector down. Why because I suck at soldering. Never had one of the water proof connectors fail.
2. I like using the braided wire coverings. I think it looks better than the plastic convoluted wire cover.
3. I use welding cable for the pos and neg battery cables. I think single "0" cable? Per the electrical gurus I used work with the welding cables have much finer wires and they transmit power much better than typical cables you find at parts stores that have larger internal wires and few wires.

[MikeB]

Originally Posted by LS short box

Couple more things I like to do wiring wise.
1. I will not use those cheap red/yellow butt connectors or male/female spade connectors.
I go to Fleet Farm or Fastenal and get the connectors that are the waterproof heat shrink type that have some type of "goo" inside that melts as you heat shrink the connector down. Why because I suck at soldering.
2. I like using the braided wire coverings. I think it looks better than the plastic convoluted wire cover.
3. I use welding cable for the pos and neg battery cables. I think single "0" cable? Per the electrical gurus I used work with the welding cables have much finer wires and they transmit power much better than typical cables you find at parts stores that have larger internal wires and few wires.

1. Yeah, the hardware store crimp-type butt connectors aren't very reliable. Haven't used the heat shrink, low-temp solder type yet, but that seems to be the way to go for butt, ring, or spade terminals. If I run into a situation where I must use the old crimp type terminals, I use the middle "tooth" of the Klein #1005 crimpers in the photo below. I've yet to see a wire pull out of one of these crimps. Good source for terminals and info, along with other stuff:https://www.delcity.net/store/termin...tor-lead-free/

2. Ditto on the braided wire covers!

3. My battery cables are 2 gauge, which is more than enough to handle a starter. They had been 4 gauge and worked OK, but the 2 gauge cables let the starter spin like the spark plugs are removed! For a trunk mount battery, guys seem to like zero gauge.

[kwmech]

Mike, what's the application for the coolant recovery bottle I see there

[MikeB]

Originally Posted by kwmech

Mike, what's the application for the coolant recovery bottle I see there

75-79 Nova, Ventura, Apollo, Skylark

OER #551448 tank, Dorman #82590 cap, and a silicon hose

https://www.oerparts.com/product/551448.html

You can probably mount it farther back than mine. I didn't want to mess with the mega-fuse block and wire, and I was able to use an existing hole.