Engine wiring harness vendors

[bigunde]

I just purchased an 83 Chevy C-10 4x4 long bed. I'm pulling the 305 out and installing a 454 and would like the correct harness. Thoughts on who to buy from? Thanks

[liftlawssuck]

Not sure how much different they are form one another but you can use the one for the 305. I prefer to make my own based on original harnesses. I take an original harness and rewire it. I've installed a few aftermarket ones and it's just not worth it to me any way. Too much fit and finish and it never seems exactly the same as original.

[Prong]

I'd try M&H or American Autowire. They both get good reviews.

[franken]

I'm pretty sure the underhood is still two harnesses on squares. They're different depending on options such as engine and guages or idiot lights, etc. Try wiringharness.com (M&H) to start and many vendors sell the same harnesses so you can shop around.

[hatzie]

There's not too much to the engine wiring on these trucks.
GM used Crosslink Polyethylene wire jacket in these trucks so the wires are usually in reasonable shape.

There isn't an engine harness per-se... more like several individual wires. You have the following on the engine.

1. Oil and Temp sensors for the gauges or lamps. Two wires.
2. HEI Tach and Power. If you have tach it's two wires. If not it's one.
3. Alternator... charge, sense, and excite wires.
4. Starter... Crank, J-Stud feed, Bulkhead power feed, and sense wire to the alternator. And the fat electron hose from the battery.
5. The single AC compressor power wire that runs from the Low Pressure Cutout switch and wyes to the idle kicker solenoid.
6. Ground wire from the battery on the alternator bracket.

The forward lamp and horn wiring is the closest thing to a harness in the engine bay. It's six wires plus some grounds to the rad support. If this is damaged you can pull it out and lay it on a sheet of plywood and lay out replacements for any damaged wires.
The wiper motor and heater/ac are technically separate individual harnesses. Not too many wires in either. You can unplug them. lay them out on the bench and install replacement wires with new terminals if needed.

I often see butchered rear lighting wiring harnesses if you want to call them that. This is the tail lamp wires to the rear of the frame. For some reason trailer installations meant popping on Scotchloks or chopping off the wires and adding open butt connectors that turned the wires into a green corroded mess. It's four 16ga wires with Packard 56 terminals on the bulkhead plug end and Weatherpak terminals on the tail end... LH Turn/Brake, RH Turn/Brake, Backup, Parking. I usually add un-terminated Blue and Orange 12ga wires with 16" or so of slack on the forward and rear ends for trailer brake and trailer breakaway battery charging. You re-use the bulkhead plug end and replace the pre-1983 molded plugs with the 1983 and later Weatherpak.

The cab harness is more of a real wiring harness... they're fairly specific to the options in each truck. GM factory staff must've had a real picnic keeping track of these on the line. I generally repair these so I don't loose functionality.
Even inside the cab there are bundled sections of wiring that are separate. Like the NL2 dual tank switch wiring, power windows, power locks, the dome light, and cargo light.

[hatzie]

The Painless etc harnesses are anything but. You'll get just as familiar with crimping Packard 56, Pak Con, and Weatherpak terminals on one of these harnesses as you would just plain repairing yours.

The PVC (Poly Vinyl Chloride) jacket General Purpose wire sold at most auto parts stores is just plain garbage. PVC gets brittle at temps below 30°F and progressively more brittle as the temperatures drop below that. I use Crosslink Polyethylene (SXL, TXL, GXL) wire for all my repairs. The GM wiring diagrams specifically state SXL and GXL in several places. SXL is the heaviest thickness jacket so I typically just default to that. You can get small assortments in 25' coils on evilbay. The larger outfits that sell to the public like Waytek and Del City sell in 250' and 500' spool minimums.
As far as wire colors goes... Crosslink poly wire in many primary colors with various color tracer stripes is available on evilbay along with the more common solid color wires in several gauges.
A Brady BMP21 label printer is quite tough and it can be purchased at Home Depot. It runs for quite a while on 6 AA cells. It'll print wraparound adhesive labels for the ends of individual wires or the split poly or mesh sleeve just behind connectors. I use the nylon cloth label cartridges.

Tools to crimp a wide range of connectors aren't terribly expensive. Here's part of my post from my 2005 2500HD build thread.

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If you do any automotive or motorsports electrical work you do not have to buy the crimp tools that crimp the pins for one connector family only in one operation. That type of tool is real nice but it's expensive and not versatile.
Delphi made two very versatile ratcheting terminal crimp tools that are inexpensive for pro level tools.
They crimp terminals in two operations. The conductor is crimped in the proper cavity for that terminal & wire gauge. Then you move the partially complete assembly to another cavity where the insulation or seal wings are crimped in a second operation.
I've crimped Deutsch DTM & DT open wing terminals, Molex GT, Metripak GT, Metripak 150 & 280, AMP Quadlok (VW AUDI), Weatherpak, Packard 56, and several other families on 14-20ga wires using the two Delphi tools. $220 for the pro level tools is a bargain for that versatility.
They cost between $90 & $130 each but you can position the terminal and ratchet the tool down and re-position the wire without loosing the jaw closure. They will not open til you have completed the crimp cycle or cammed the emergency release open so you don't end up with an over or under crimped terminal. You can likely evilbay these off for $95-$100 each if you take care of them and suddenly decide you don't need em.
-Delphi Ratcheting 12085270 Crimps Weatherpak and Metripak 150/280 sealed terminals... Three seal and two conductor wing cavities.

-Delphi Ratcheting 12085271 Wide range crimper with five cavities for conductor and un-sealed insulation strain relief crimp wings.

If you need to crimp Metripak 480 or 630 or Packard 59 terminals you need larger cavity tools but the above tools will crimp 85-95% of what you're likely to encounter.

These are some less expensive $30ish non ratcheting tools. These are great for the weekend warrior that's crimping a few terminals or as a tool to hold you over til you can find a nicer one. You'll tire of them quickly if you're building vehicle harnesses for your hot rod or restorations. One downside is you can open them before the crimp operation is completed and end up with loose crimps and they don't have the positive stops of the more expensive tools so you can over crimp the terminals as well. They also tend to wear faster than the pro level tools.
-Wire and weather seal crimp tool for Weatherpak and Metripak 150/280 sealed terminals. https://www.amazon.com/dp/B002CCAEJ6
-Wide range wire and jacket wing crimp tool for unsealed and sealed connector conductor wings. This tool will not crimp the Weatherpak/Metripak/Molex-GT weather seals but it will crimp the conductor wings of those families and both wings of un-sealed terminals. https://www.amazon.com/Delphi-Packar.../dp/B003MWJ6SA

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DO NOT throw out the plastic connector shells. Many of them are obsolete or very difficult to find. The terminals inside are usually fairly easy to find.
You need to identify what terminal family you're dealing with. The GM wiring diagrams have the connector shell part numbers in the diagrams.
A very helpful individual has already put together a long writeup about re-using connector shells here. http://www.rowand.net/Shop/Tech/Reus...iringPlugs.htm
This is his terminal identification page. http://www.rowand.net/Shop/Tech/Auto...Connectors.htm

GM Service Training Group put together a color booklet on terminal extraction and crimping. I scanned it and posted it in the 73-91 manuals.GM_STG_18001_02_VA_Wiring_Assembly_Repairs

[MikeB]

My 82 had a least a couple poor connections in the bulkhead connectors. I cleaned them with a burnishing tool and contact cleaner, but still had intermittent problems that I could fix by tapping the bulkhead connector. Also, my fuse panel had some corroded contacts due to water leaks near it.

I couldn't swing the $$ for a "exact fit" harness kit, so bought a very nice generic kit by American Autowire. It uses cross-linked wire, with most (if not all) wires one gauge larger than stock. They even included a charging kit with a maxi-fuse holder and 6 gauge wires! But it did require a ton of work, several modifications, and LOTS of prior experience to get it installed. I had wired a 66 pickup, a 55 Chevy car, and a 37 Ford hot rod, and this was the most challenging because of things like the wiper/washer connectors and instrument panel connector.

But it works great. Voltage drop from the battery to headlights and ignition is around 0.1 volts, whereas before it was a 1.0-1.5 volts! Headlights are so much brighter that I scrapped the idea of using relays. Also, My HEI obviously has more current to the coil. Also, the dash, brake, and tail lights are brighter.

[hatzie]

You can extract and replace the trouble terminals in the bulkhead plugs. It takes a few minutes rather than a few days.
The narrow ones are Packard 56 and the wide ones are Packard 59.
Corroded power feed terminals at the starter, bulkhead plug, ignition switch plugs, and the J studs on the firewall are a lot of your voltage drop.
Replacing all of the red circuit 2 wires with the next larger gauge won't take nearly as long as installing a full harness.

[Danmcg]

Thanks again for the great info Hatzie!!!

[MikeB]

Originally Posted by hatzie

You can extract and replace the trouble terminals in the bulkhead plugs. Corroded power feed terminals at the starter, bulkhead plug, ignition switch plugs, and the J studs on the firewall are a lot of your voltage drop. Replacing all of the red circuit 2 wires with the next larger gauge won't take nearly as long as installing a full harness.

Hatzie, you know your electrical systems!

Good ideas above for most trucks, but in my case I was still dealing with a corroded fuse panel. I'm not sure if the fuse terminal buses can be replaced, but if so, that might have been worth looking into.

I will say I'd rather have the OE bulkhead disconnect than the engine compartment wires soldered directly to the fuse panel. But the upside of direct-connect is lots fewer connections to worry about!

As for replacing the two red panel feed wires, on my 82 they were metric, somewhere between 10 and 11 gauge, which is step above older trucks that used a single 12 gauge wire. So, not too bad. But #10 would be the best replacement size.

I ran a single #8 wire from the starter BAT terminal through a maxi-fuse to a stud mounted next to fuse panel. I then branched off there with #10 wires to the fuse panel BAT bus and the ignition switch. The kit had used a single #10 panel feed wire, but I had a roll of #8 SXL wire, so why not?

The 20-circuit fuse panel was overkill for my basic truck, but has lots of room for expansion. Four of the extra circuits connect to a 4-pin connector via #12 wires.

[hatzie]

We haven't been manufacturing a lot of stuff in this country for a long time. What passes for 10AWG 12AWG etc is likely mm² now. Just like plywood and dimensional lumber is actually metric now too.

The fuse panel is mostly filled with Pak Con terminals.
I've never purchased bussed Pak Con terminals. I know they still come in the Pak Con ATC/ATO "add on" fuse blocks like the units Polaris uses on their ATV and UTV. The Pak Con bussed fuse blocks, like the one pictured below, are around $10 so you might want to do some digging. I bet the bussed terminals can be found at least in four and maybe five and six terminal strips.
You can buy the individual Pak Con fuse panel terminals. I'd be sorely tempted to solder the individual terminals to a strip of copper thereby manufacturing my own bussed terminals.
Since terminals on a reel to load in a machine are bussed together on a plated or just plain brass or copper strip... you could buy some "reel" packaged terminals from Mouser Electronics and verify if the reel spacing is the same as the fuse panel spacing. I bet that's why Delphi Electronics chose the fuse spacing they used in those fuse panels. Why buy special terminals when you can buy something already in circulation.