Building a wiring harness...

[steved]

I've seen reference to the special connectors (Douglas)...I'm looking to redo my wire harness, is there anything keeping a DIYer from making their own harness?

I'm only concerned about connecting to the switches, guages, etc...not the wire-to-wire connections. I'm not looking for a full restore, this truck will be a daily driver.

I intend to use stranded THHN wire for the harness, keeping the existing hardware (switches, lights, etc.).

[Cal_Gary]

You can go your own way if so inclined-I'm just finishing up a complete rewiring with a Painless Performance kit and the gauges are the cog in the wheel-haven't gotten them working other than the battery gauge. All else works great!

Douglas versus Packard connectors are based on the year of your M-I recall Douglas connectors are the metal shells that were on the early series....
Gary

[monkeymissile]

Packard style are the newer rubber connectors

[refit1701]

I had a harness made which is an exact duplicate for my truck, and it has the Douglas metal shell connectors. I got sorta chewed out at Aberdeen by a vendor "why would you use those when you could have used the newer Packard rubber ones?". If you're not going for a period correct rebuild, do the Packard connectors, it will save you some heartache.

[MSeriesRebuild]

Packard connectors are no easier than the Douglas type. In fact they are worse to deal with years down the road when it's time to unplug them. Packards are no easier to install & are more costly than Douglas when buying individual parts. We have made many custom harness without waterproof connectors, work great, less costly, faster to assemble, etc. Many plus marks if you don't really need the waterproof.

[Cal_Gary]

Well John, the vendor should know that it's your truck and you can do it your way regardless of what the vendor's opinion was. You might have said, "ok provide all of those connectors and harnesses for free and I'll happily use them!" My M will never be a 100 point winner-it looks like an old Army truck (since it is) and I make absolutely sure it is 100% safe, even if I use a 12V system, civilian wiring and so on. Don't let anyone get on you for your choices-nobody else knows what your budget, time constraints, etc. are, and as long as nobody is pointing out an obvious safety issue that needs to be addressed, they should hold their opinions.

Just my 2 cents,
Gary

[steved]

I guess my question is this: are the connectors (either/or) required to make the wiring work? Or are they just terminating connections between harnesses? Can they be eliminated?

Again, I have just pulled this thing out of storage, haven't really looked into the details yet. But I seem to think my particular truck has a mix of parts...I think it has both metal and rubber connectors.

[MSeriesRebuild]

I guess my question is this: are the connectors (either/or) required to make the wiring work? Or are they just terminating connections between harnesses? Can they be eliminated?

Again, I have just pulled this thing out of storage, haven't really looked into the details yet. But I seem to think my particular truck has a mix of parts...I think it has both metal and rubber connectors.

It's common to see both types of connectors on the same truck, especially if solid-state turn signals or composite lights have been added. You are correct in that many connections are not absolutely necessary if it doesn't matter to you. We sort of look at it with the point of view of ease of maintenance down the road. Many times it's handy to have a connection if you simply need to unplug or isolate a circuit at some point. On our custom harness, most of the time we add more connections than original with this in mind, it's a big help if the need arises, especially for a person who may not be as familiar with the system as we are.

[steved]

I was planning on keeping the "connections" but eliminating the "connectors"...there are other modern alternatives to the period-correct versions (which are plenty pricey).

You make a good point about isolating circuits, probably also makes it easier to make the harness in pieces.

[MSeriesRebuild]

I was planning on keeping the "connections" but eliminating the "connectors"...there are other modern alternatives to the period-correct versions (which are plenty pricey).

You make a good point about isolating circuits, probably also makes it easier to make the harness in pieces.

We build ours on the bench, then put it in split loom as 1 piece. It's then ready to install.

[steved]

For you, that would work since you already know the dimensions, but for the DIYer that is doing the one and only he has...pieces would be easier (build it on the truck as you go).

[MSeriesRebuild]

For you, that would work since you already know the dimensions, but for the DIYer that is doing the one and only he has...pieces would be easier (build it on the truck as you go).

I'll have to disagree on this one. I did some on the vehicle wiring years ago, actually it created a monsterous mess of wires that looked terrible. We don't have patterns either, would be of little use since every truck that gets custom built harness is different, sometimes vastly from original. Here's the way we do it. Pull out all the old harness, figure out the single longest wire that is part of the front main harness. Pull this wire along the path you want the harness to run & tie off both ends at the correct spot. Now look along the path of that wire to see where other wires in that harness need to terminate along the way. Place a piece of masking tape on the lead where other wires need to turn out. Measure the distance from the turn out to the connection point & write the info down. Once you have all necessary leads on your list, pull the longest wire back out, build the rest of that harness from the measurements made & attach the other wires to the main wire turning out the proper length of wire according to the taped markings on the main wire. It's very simple to put together, install the correct end terminations & correct diameter split loom. When installed in the truck, it's nice & neat, easy to attach to hangers & tie off with zip ties elsewhere. You can make the rear portion of the harness the same way with connections for the front & rear section where ever you choose to put them. When all is done, it looks & functions great for many years. All we ever did using the 1 wire at a time method wound up looking like a rats nest maze of wires with no order what so ever.

[g741]

Hi Guys: One really inexpensive way to go when replacing your wiring is to use one of the front and one of the rear harnesses that I have. They were made in Europe and are an exact match for the M37 vehicle. They do not have the little metal tags and the wires are color coded. They utilize the Douglas connectors. All in all a good inexpensive way to put a new harness in your vehicle with wire that has good insulation. And you cannot beat the price - $30 for the front and $30 for the rear. Plus all the good advice and drawings that I have. Sid

[steved]

I also found a cheap way to get multicolored wire that is the better automotive grade wire...

A friend of mine has a couple wiring harnesses left over from swapping a 12-valve Cummins in place of a 24-valve Cummins in a dodge truck...he's going to give me the extra harnesses! that should provide good wire for the engine and dash, and I should only need to acquire enough wire to run the rear section of the frame.

Sid: can you PM me some information or a link to your site?

[knattrass]

Sid is the way to go... you'll save yourself a ton of questions and his stuff is good to work with. Nothing like clean wires after digging the old one off the truck.