New Wiring Harness

Most of my vehicles are much older than my CUCV, and whenever I acquire something new I always replace the wiring harness as a matter of course. Always. I didn't once, and ended up on the side of the road in the Arizona desert in July with the charred remains of a minor engine fire hacking together a replacement for the burned section of harness out of some trailer lighting wire. I've seen so many hacks and electrical fires in my cars and others' that I don't care to repeat those mistakes. Additionally, installing a new harness is WAY easier than trying to track down a grounding wire hiding somewhere deep in the harness or something and you practically eliminate the possibility of future electrical issues for a few decades.

On cars where quality aftermarket harnesses are readily available, I'm more than happy to go the easy route. When that's not the case, it becomes necessary to make a harness. This takes longer, but is a lot of fun (assuming you're into that sort of thing) and gives you the opportunity to modify things a bit.

The electrical system on my M1009 is pretty well trashed. Some things sort of work, but I haven't found much electrical that fully works as expected that I didn't recently replace or rebuild myself. Most everything that isn't steel in my truck has all but turned to chalk, so instead of trying to track down and terminate the gremlins one by one just so they can continue to breed and multiply in the chalky insulated recesses of my truck, I'm going to shotgun the thing and make the electrons happy.

Since the civilian harnesses all include power windows and that sort of thing, I really don't care to go that route. The military replacement harnesses will be 30 years old, stiff, and also have a bunch of junk I don't need (the truck is to be a workhorse, occasional off road rig, and occasional daily driver, so blackout lights are kind of silly). I don't think there are any harnesses available for civilian market trucks without any power accessories, AC, and the like. That means I'm pretty much on my own. This is NOT a bad thing!

Since I'm going to be starting from scratch, I'm going to engineer in a little extra longevity and reliability. That means relays for all the switches, breakers, a full compliment of useful instrumentation, the whole nine yards. I'm also on a bit of a crusade to eliminate as much plastic from the truck as is practical. That means a custom grille, in which I intend to change up the headlights a bit and add a second set of primary driving lights inboard of the two in the stock position. Finally, and I still haven't fully figured out what and how, but I intend to replace the plasticky stock switches with quality steel rockers where feasible.

I have a few more things to do before I get too deep into this project, but between the weather this coming week and waiting on parts and tools to arrive I will likely be able to find the time to get started on the schematics. I thought it would probably be a process that would be enlightening to some, and maybe even useful, so I'm sharing it here.

Thanks for sharing,looking forward to reading about your project.Are you going to keep it 24v.starter? I imagine going 12v.would really make things easier.

Going 12V. Already have the starter, and the only reason it's not already 12V is because I wanted to get the truck running before I introduce any additional variables and to thoroughly familiarize myself with the vehicle, the engineering vernacular, layout, etc. I'm probably going to keep the alternators and run the ground wire from the DS alt to an intake stud or something. I'll run one, and when it dies sell it as a core and use the second as a replacement. That is, unless someone makes me an offer for the mil-spec units that tilts the economics in favor of just buying an off the shelf unit.

Any suggestions for gauges? The stock gauge assembly is crumbling like wet chalk, and it needs to be gone ASAP. I'm probably going to fab something up in a more or less stock shape, but with more useful things in a more useful arrangement.

I feel the same way as you do. I have been mocking up a new gauge cluster using auto meter gauges. I will keep the 2 bulbs for the gens but move them below my speedometer. I have already ran a second 12v fuse panel were I have mounted my fuel pump on a toggle. I was drawing up the circuit today were I have a control curcuit feed my relays on my power toggle. I will have a relay for gauge power and fuel pump. I can daisy chain as many relays as I want on that switch. I am going to start a gauge cluster build thread.

A little insight into my specific process:

Obviously, it helps to start with a pretty comprehensive understanding of automotive electrical systems. Using this knowledge, stare at the schematics for a while, stare at the truck itself for a while, press buttons, use your multimeter if you need to (this is the most important tool for this sort of job) and get a thorough understanding of what everything on the vehicle does. Older cars (CUCVs are on the border of this classification) have very simple to read component map-style schematics. These are great for helping to figure out macro-level things, but suck pretty hard for the minutiae. Fortunately (and this is a big part of the reason I bought this particular vehicle), there's really not a lot of minutiae to have to decipher. They're really pretty simple. Black boxes are few, and the only really big ones are the glow plug card and the low coolant module card if you ignore the diagnostics circuits.

Once you are confident in your understanding of where the electrons are flying in your truck, it's time to get creative. If you're sticking with the stock setup and just want to get rid of all that chalky wire insulation waiting to blow fuses and start electrical fires, you can skip this part. Otherwise you're about to perform a major upgrade, so you might as well maximize your wrenching miles! Do you want to have a bunch of driving lights Baja style? An in-house system? Huge obnoxious stereo system with a jiggawatt of bass and no other discernible timbre? This is where you design that in. Personally, my intent with this rig is for it to be a workhorse to haul around other project cars and parts, off roading/camping on occasion, and daily driver duty in the winter and when I otherwise feel like it. Design parameters focus on reliability, fuel efficiency, and finally performance in preferential order. The electrical system has a hand in all three sections. For reliability, I'm simplifying, adding relays, swapping fuses for breakers, removing anything I feel is unnecessary, and using the highest quality parts I can find to fit the application (this will have marginal effects on the other two parameters). For fuel efficiency and performance (which are often one in the same), I'm adding full instrumentation and getting rid of the stupid idiot lights. If you have a whole corps of mechanics and a whole fleet of vehicles, I guess idiot lights keep soldiers focused on the task and not how the vehicle is doing, but I need to know what's going on in my engine compartment. Finally, a wise man knows he doesn't know: I'm going to leave some room for future expansion. I don't know what that might be, but I'm pretty sure it's going to happen at some point. I do intend to add a house system for camping down the road, but I intend to keep that thoroughly isolated and separate. Finally, I've been thoroughly unimpressed with several features that were engineered into (and often out of) this truck... I don't know if it was the '80s (the automotive dark ages), GM using the cheapest crap they could find, or the long term desert storage, but the plastics on this truck are far worse than any I've ever encountered, and most of my vehicles have been at least twice as old. I'm on a thorough crusade to eliminate all plastic components I can. That means getting rid of the special GM plugs and switches wherever possible, I'm fabbing up a replacement cover for the transfer case shift lever (and getting rid of the two wires that come out of it instead of routing along with everything else), I'm probably going to ditch the vast majority of what's on the steering column, I'm fabbing up a gauge cluster, I might even get rid of the stock tail lights and fender-mounted turn signals... I got a bunch of steel stock at the recycler, and once I finish with some mechanical issues I'm still wrestling I'll start in on those tasks.

Once you know what you want to do, it's time to map components. I prefer Adobe Illustrator, but I'm an occasional graphics guy so that's easy for me and available. Here's my map as it stands:



I essentially printed up the schematics from the TM (actually, I used the colorized version posted here by another benevolent user because they're easier to read without needing to break out a stylus), and I circled every component I wanted to keep, and exed out everything I didn't. Then I simply made a component map. I wanted everything on one page for simplicity's sake, and I wanted to keep it a simple component map style since I'm going to be eliminating all the black boxes anyway. You'll probably notice that all the switch gear is totally different, there's an extra set of headlights, a bunch of parts are altogether missing, and so on. That's MY schematic so far. Yours will undoubtedly be different. I'm still fine tuning a few things... I might move the coolant temp sensors around a bit, maybe change up the switches a little still, and so on. I was sure to label all of the parts, and in some places labeled the leads as they were hooked up on the TM schematics.

The next step (just to get you thinking and ready for it) is to start placing the wires and plumbing it all together. Some of this will be fairly straight forward, some can be lifted straight from the original schematic out of the TM, some will require Googling the installation instructions or schematic drawings of various components, and for some of it I'll actually need to buy the components to know exactly how I want to wire them in.

Awesome!! I am really looking forward to your updates to this project as I plan on doing the exact same thing on my M1008A1 (BTW...this is my first post on this site �&#56397

This looks like a GREAT project! I am one of the lucky few who got his CUCV with an unmolested, and in pretty good shape electrical system! One of the things I am going to do over the winter is collect parts to redo my dash w full instrumentation. For my 6.5l turbo install I wanted boost and EGT gauges as this is my first turbo motor. I went w Speedhut gauges and I CANNOT say enough good about the quality of their product!!! They are fantastic! First is all the options they have in customizing your gauges, "font" style, tick mark style, pointer and backlight color...amazing! In some cases if they dont have what you want, give them a call and they can make it! They are not the cheapest, but quality isnt. The line I have chosen to use also have built in, setable idiot lights! As a bonus, they are made in America! They have so much using the search feature on their site is a must! It can be a lil confusing at first but once you get the hang of it, its real easy to find exactly what you want. I have always with my cars in the past used Autometer stuff, which is VERY nice, but now that I have some Speed Hut stuff in hand...they hands down blow Auto meter away IMHO.

I like where your headed. I've wanted to do the same. subscribed