Start digging around or buy a complete harness???

[Steve Goetz]

Hello!

I'm new to this forum, so thanks for the information! Recently picked up a '82 C20 350 Camper Special and it has a number of electrical problems. (No turn signals, backup/brake lights, battery drain of some type that I have not been able to run down after some minor tests, multiple bare wires under dash from previous modifications, etc.)

My question is this. I think I can get a complete wiring harness for this for about $350. Would you suggest I "bite the bullet" and buy this and redo ALL the wiring or would you spend some time troubleshooting the problems and see if its repairable without spending the money? I've done some very minimal troubleshooting and can't find what causing the drain, but I think it might be a ground issue. Battery has been tested and the alternator is brand new.

Does anyone have any experience with these aftermarket wiring harnesses and if so, a good supplier that you'd recommend?

Thanks in advance!

 

[Dmack]

Your call. Dealing with existing butchered wiring sucks. You never know what the P.O. thought was safe and works. Mine was butchered during a diesel to gas conversion. I ended up going to a scrap yard and pulling an intact harness out of a donor. Plug and play. If you try to use a universal harness, you will have problems with things like the heater, which use step down resistors to control speeds. Not sure if he is here, but on the 67-72 forum, member gmmachinz (I believe) recreates factory harnesses.

 

[AuroraGirl]

@gmmachinz I am pretty sure he lurks

 

[eskimomann209]

@gmachinz is his name. And he’s active.

edit.
id fix mine. But short of that. I’d buy Gs. The Ac harness is pretty much separate you can unplug it from the fuse panel and run the rest of the stuff to Gs fuse panel or do as recommended and buy a JY one still keeping your ac setup if it’s functional.

 

[Matt69olds]

Unless it’s really hacked up, I’d repair it. In my experience, most early cars have wiring ADDITIONS, things like add on stereos, driving lights, gauges, etc. People usually leave the factory wrapped harness alone. I’d start with tearing out anything that isn’t in the factory wire wrap and see what’s left. These trucks aren’t that complicated, the wiring is pretty simple. Once your at a good repair starting point, get a good wiring diagram and a magnifying glass. The wiring diagrams are black and white, and the entire harness is printed on one page. I love working with the new service manuals. Each diagram is in color, and only the circuit your working with is printed.


Unless you buy a factory reproduction harness, your still going to have to make wire connections. Aftermarket harness require you to make connections for the gauges, heat/A/C, optional equipment, etc.

 

[gmachinz]

Here’s an example of one of my underdash/fuse panel assemblies-this one has provisions for built-in headlight relays near the fuse panel.

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[Steve Goetz]

Here’s an example of one of my underdash/fuse panel assemblies-this one has provisions for built-in headlight relays near the fuse panel.

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@gmachinz could you email me a price (along with whats included) to [email protected]? I'd appreciate the option. Still not sure what my plan is until I start digging a bit, but your option may be my best approach. Thank you!

 

[AuroraGirl]

Here’s an example of one of my underdash/fuse panel assemblies-this one has provisions for built-in headlight relays near the fuse panel.

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found him. this is the guy we were mentioning for harness work. seems to be high quality stuff. ill eventually be getting some tail light harness from him. i wish he had a store front.

 

[AuroraGirl]

@gmachinz could you email me a price (along with whats included) to [email protected]? I'd appreciate the option. Still not sure what my plan is until I start digging a bit, but your option may be my best approach. Thank you!

they may seem to be steep pricing, but truthfully you are getting quite the wiring wonder for a price i imagine was darn near cost if you or i tried to make one. not including labor

 

[hatzie]

Wiring is oogie boogie spaghetti OOOH Scary til you think about it in a calm rational manner...
It's not spaghetti and it's not scary.

Hopefully this will begin to demystify this.

The first rule of repairing wiring is to break it up into bite size chunks and fix what's broken.
GM made these vehicles with several sub-harnesses with the most complex inside the cab.
Most every harness outside the cab is fairly simple. This was to make assembly easier and it works in our favor too.

What Wire To Use.
The crap The Borg sells is Poly Vinyl Chloride. PVC shatters and cracks at temps below 25°F and it doesn't remain pliable after repeated hot-cold cycles.
Use Crosslink Polyethlylene wire. If you look at the GM wiring diagrams most wires include SXL along with the color, circuit number, and square mm or American Wire Gauge. SXL is heavy Crosslink Polyethylene.

Here are some of the small harnesses outside the cab off the top of my head. There are more but this gives you an idea of how to break it into pieces for repair.

Lighting sub harnesses.
1- Forward lighting and horn. Five circuits and grounds to the radiator support.
If you need to replace the side marker sockets you can get 168/192 Peanut Bulb socket repair pigtails $8 for qty10 on Amazon and Evilbay. Solder and heatshrink them on with Marine Heatshrink that has the hot melt glue on the inside.
2- Rear lighting and fuel sender. Five circuits... in two sections. Seven wires front to back if you add two 10ga wires for trailer battery and trailer brake. The actual lamp harness is essentially a set of lamp pigtails that connect to a four wire connector at the rear of the LH frame rail. You can buy the lamp harness from several sources but you generally have to add the frame termination. The frame section is literally four wires terminated with a square Weatherpak or Packard 56 terminals in a round molded rubber plug and Packard 56 terminals on the bulkhead plug end with the fuel sender wire branching out near the front.
I usually upgrade the rear lamps on 1982 and prior trucks to the 2x2 square Weatherpak for reliability.
For the fuel sender wire I usually just buy a too long Chevelle, Skylark, LeMans, Nova, ... fuel sender wire to get a new female molded pin plug and I cut it to length and terminate the bulkhead end with a Packard 56 terminal to insert into the bulkhead plug. This wire is the same for single and dual tanks... this is the sender disconnect on NL2 dual tanks.

Engines
Usually don't have a harness per-se. The wiring on the engines is a conglomeration of several simple sets of wiring with split poly sleeve to protect them somewhat from the heat.
HEI power and Tach (if you have a tach).
Engine sensors. Two wires... Temp and Oil Pressure.
Alternator. Excite, Sense, and 12ga Charge (BAT) wire. Sense and Charge wires are run to the starter or the Junction Studs on the firewall through fusible links depending on the year.
The wire to the AC Compressor is part of the heater sub-harness.
Starter Crank
Junction stud and bulkhead plug power from the Starter... Two or three RED 12ga wires with fusible links.

Heat and AC
Is a fairly short and not terribly complex sub harness with several obsolete connectors that still have terminals available... with a long dangling green wire with a molded connector for the AC LPCO switch and a longer green wire to the AC compressor and high idle kicker on AC trucks.

NL2 dual tanks
is a pair of sub-harnesses with a firewall disconnect that also connect to the production fuel sender wire, as noted above, and several other points. 1987 and later TBI gets a little more complex but not much.

ESC, if you have it and you want to keep, it is another small sub-harness.

You get the idea. I hope.

Connectors
You need to know what connector family or families you're dealing with to order the metal terminals... The connector part numbers are in the wiring diagrams so you can usually google them and find out what they are. You'll often find the connector shells are obsolete... I save connectors in tubs so I can use them to repair burned up connectors.
You'll find a lot of plastic female connectors that plug into 1/4" wide blades and a few of the male half. These are Packard 56 terminals. The slightly beefier and wider Packard 59 terminals are the same animal just higher current. These are not sealed connectors. GM used them in the bulkhead plugs on the firewall. You'll find some specialized versions like the female Packard 56 with a slot cut for the Nailhead coolant temp sensor.
GM ATC/ATO plastic fuse blocks use PAK-CON and Packard terminals.
Glass cartridge fuse panels are a little more difficult to source connectors for but you can probably track them down.
Weatherpak... Google it you'll immediately recognize them.
Metripak... These come in sealed and un-sealed and are available in four sizes. The plastic connector shells themselves are usually specific to the sensor or control unit they're plugging into so a lot of them are obsolete... save the connector.

Wiring Diagrams
You can download the GM wiring diagrams and scale some of them up so you can read them. 1973-1986 are on 12x36 or 12x38 banner pages so your larger page sizes are limited. From 1987-1991 GM used comb bound Tabloid (11x17) pages. Tabloid pages can be scaled up and printed on ARCH B (12x18) sheets of paper.
BTW: GM made a complete disaster of the 1987 wiring diagrams. If you have a 1987 I'd try the 1988 diagrams because they are mostly the same but actually readable.

Some other thoughts on processes...
There's nothing exactly the same as the harness your truck or car was born with. I always fix it if I can.
Even pretty chopped up harnesses can usually be repaired by replacing damaged individual wires and re-installing. If you're looking at replacing the harness completely you're going to pull it out anyway. Get a notebook, Sharpie, painters tape, and your digital camera. Everything unplugs or has a ring terminal under a fastener. Mark every connection with tape and sharpie. Take huge numbers of pictures so there's no question where they go and how the harness was originally routed.

Many of the original connector shells are obsolete. The terminals are usually not obsolete so you can re-use most if not all of the old connector shells with new terminals and new wires where needed. USE proper terminal extractors, they're cheap... as in $3-$9, and learn where the terminal locks are in the parts you are servicing so you can save the connector shells. You can download the Delphi GM electrical connector manual that outlines this information with pretty colored pictures.

If the harness has enough damage that it needs more than two or three patches and I figure it might have hidden damage I just pull it out of the vehicle.
I usually lay the harness down on a sheet of plywood with a 2x2 along the long edge that's large enough that I can splay out each connector and leg so it's not an obnoxious pile of spaghetti.
I put large head small shank nails in the board where the harness makes bends, or there are bundle or wire exits, and near terminations so I can tie the wires in place with nylon wire ties. Get a thousand or two or three of the narrow wire ties for this and bundling the new and old wires together to wrap... you can cut the ties off and install new ones as you insert new wires. It makes it much easier to test and lay new wires into wiring bundles that aren't a convoluted mess. You can pick up the board with the harness attached and lean it against the wall with the 2x2 against the wall if you need space while waiting for parts. The 2x2 keeps you from crushing the harness between the wall and the plywood.

Once the harness is laid out you can evaluate how bad or good it really is. Most aren't as bad as folks think they are.
I carefully examine the harness for damaged areas and mark the damage with chunks of painters tape.
I look at the wiring diagrams for the correct wire gauge and color and I install the same color and the same or larger wire gauge using new terminals where I'm replacing damaged wires.

Harness Wrap
DO NOT wrap the wiring in electrical tape it'll become a gooey sticky mess in a year or less. If I cut away a long section of the original harness wrap tape in an interior harness I replace it with split mesh harness wrap for abrasion resistance with rings of textile harness tape at 4" intervals and I wrap the wyes with textile harness tape as well. It looks professional and it keeps the wires safer than the original. You're not taking this to Pebble Beach you want your repair to last.

 

[hatzie]

If you do any automotive or motorsports electrical work you do not have to buy the expensive crimp tools that crimp the pins for one connector family only in one operation. That type of tool is real nice but it's usually super expensive and not very versatile.

Delphi made two exceedingly versatile ratcheting terminal crimp tools that I've used the hell out of over the last 35 years or so both at work and home.
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 (@ $110 each) for a pair of 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 12085270 Crimps Weatherpak and Metripak 150/280 sealed terminals... I have used these on GT150 connectors on my ATV and several other families of sealed automotive terminals. They have three seal and two conductor wing cavities.

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12085270.jpg (44 KiB) Viewed 147 times

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

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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.

Sargent tools makes clones of the Delphi tools and non-ratcheting versions that are a serious step up from the $30 tools below.
http://www.sargenttools.com/ToolsByTrade/Metri_Pack_Unsealed_Crimp_Tool/

These are some less expensive $30ish non ratcheting tools. These are great for the weekend warrior but you'll tire of them quickly if you're building vehicle harnesses for your hot rod or restorations. The 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.
-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-Packard-F ... B003MWJ6SA

 

[MikeB]

A problem you might have is poor connections at the firewall plugs. Not much you can do about that. I cleaned mine with contact cleaner and a burnishing tool, but I still had intermittent issues.

I ended up using a very nice generic GM kit from AAW (American Autowire), but there is NO WAY I'd recommend it to someone without LOTS of automotive electrical experience. Can't tell you how many Delphi/Packard terminals I had to install (or how many I had to re-do). Also had to fabricate an adapter plate to mount the fuse panel, which does not use firewall connectors. That can be both good (no connectors to corrode) and bad (PITA to install, and virtually impossible to remove). I wasn't in a rush, but spent 3 months off and on getting the job done. If I had to estimate the hours, I'd guess it's probably in the 80 range. Definitely was not plug 'n' play.

AAW and and Painless both make OEM-type kits, but they are very expensive. And we've got our own member GMACHINZ with what looks to be a very nice kit, and it sounds like he would support you very well.

Regarding terminal crimpers, instead of spending a ton of money I used a Tool-Aid crimper kit with several different dies, including one for Delphi/Packard terminals. I've used this tool on 3 complete wiring installations, and another where I had to re-do some poor work done by a PO.

Mine is around 13 years old, but similar to this one:

https://www.jbtools.com/sg-tool-aid...MIo9jExbO26AIVh5-zCh1cwwFMEAQYASABEgKTivD_BwE

 

[hatzie]

The bulkhead plug is Packard 56 & Packard 59 terminals.
If one of them or even several are giving you fits extract and replace them.
There's some kind of cosmoline or other gooey protectant in that plug that you want to make sure you keep in place.

 

[Reinovator]

Depending on your skill level and willingness to learn is the real question. I have done new, rebuild and junkyard regardless you will learn to be a contortionist, in the cab area. leave the old in place a route as you go with new. or junk yard donor. double check all connections then check again. I don't like wiring but it seems I do it a lot. Be patient. have two new rolls of tape one to throw and one to use. Zip ties and crimp connectors ( solder works best with heat shrink tubing) you may find your problem as you are rewiring. Good luck.

 

[Snoots]

I like plug and play, not plug and pray. I'd go with @gmachinz