Wiring harness 101

Uncle Skip · Post by **Uncle Skip** » January 22, 2009, 5:35 pm

Here are pictures of the wiring jig I made from an old piece of shelving and a small used cake pan. I mounted the pan to the shelf, drilled holes for where the toggles will mount and put some open clamps on the board to hold the routed wire.
The way it works, a hot wire comes in to the fuse block and then out to the main switch (Key lock? or master toggle). On/ off. Then two out wire from the main switch then runs to two terminals [ main circuit like ignition, start,fuel pump, etc. on one side and accessories on the other terminal) on the fuse block. These two different circuits are fused to out terminals that go to toggle or regular on/ off switches in the switch panel. Another wire comes off the switch to the firewall plug and then to each circuit.... head lights, running lights, coil hot, starter, etc.
I measured all the distances from where I'll mount the toggle switches to the fuse block accounting for turns and including enough wire for the service loop I mentioned, laid it out on a board.
Here some pictures I hope will help you understand what I'm trying to accomplish.
U@ss

On this last photo, the long row of terminals are fused and go to the small wires thru the toggle, then to the circuit. The big wires carrying the power connect at the far end, one to run circuit, one to the accessory circuit.
The cover is a little piece I had laying around and I put it on just to show how I'll bundle the wires when I put them in the truck.
No rats nest, just a nice neat bundle.

DCarr · Post by **DCarr** » January 22, 2009, 8:31 pm

Nice, Skip. Sure beats fighting with spaghetti.

Uncle Skip · Post by **Uncle Skip** » February 17, 2009, 7:01 pm

Eurika, I found my gated toggle for the master switch.

Now the re-wire can proceed post haste.
If you buy them from an aircraft supply, they're $40.00 each or more.
I found some surplus ones (new) for 22.00 plus tax. If anyone needs one, let me know and I'll see if they have any left.
I bought 3.... one for Nadine and 2 more in my stash for future projects.

By way of explanation, a gated toggle is one where you have to pull the lever out to move it to the on position, but can be flipped back in the off position just like any other toggle switch.
You can't accidently put the switch in the "on" position and they are heavy enough to use as a primary switch.
U@ss

36truck · Post by **36truck** » February 17, 2009, 7:13 pm

Got a pic of one?

Uncle Skip · Post by **Uncle Skip** » February 18, 2009, 7:43 pm

Tom. Yes I do but I don't know if it will show you the difference between it and a regular toggle.
I'm just about finished with the front headlight/ turn signal wiring harness for the front of the truck. I used professional, not the cheap insulated splices and heat shrinked them all. Take a close look at the junk yard connectors.
Also, I incorporated a common ground wire that will go to the frame in the engine compartment.
The two big wires in the small connector will go to the headlight relays and are high and low beam respectively. I'll operate the relays with the original small gauge wire from the headlight switch on the floor.
The other plug has the turn signals and running (park) lights and ground wires.
The rear harness will be next and will include the fuel sender wires, electric fuel pump in with the lights. I have a special insulated plug I found just for this application.
U@ss
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truckerdaddy66 · Post by **truckerdaddy66** » February 22, 2009, 9:35 am

Hey Skip, good reading,you can buy number id rolls from your local ele. supply house .The kind you use in ele. control panels where all the wire is the same color.Great for us color blind people ,like me.

Trucker daddy, New Caney,Tx.

Uncle Skip · Post by **Uncle Skip** » August 29, 2009, 5:17 pm

Finally, cool enough for a little progress on Nadine. I took out the old wiring harness and traced out the circuits to see how things work.
I am not going to use any of the old wires. They're cracked, fatigued, broken, and filthy.
But basically there are only a couple of relative components and once you understand how they work, the knowledge pretty much applies to what ever you want to do to your own harness.

The basic circuits are turn signals, lights, brake lights, ignition and starter components, and accessories.

So I guess the turn signal switch is the most complicated unit on the truck.
I'm going to try to explain how it works. It is not connected to the light switch in any way. (exception for stock switches because the hot tap and fuse is contained in the light switch. I'd eliminate this wire if I could. Makes things a lot simpler and cleaner to wire it individually.)

*Please note that you need a double filament bulb in each light fixture in the front of the truck.
One for the turn signal lamp and one for the running lights.
Turn signal bulbs are all wired individually from the turn signal switch. If one bulb burns out, the other turn lights are not affected.
You need a fixture with one single filament bulb for the brake light and one double filament bulb for the turn signal and running lights in the rear.

*Power to the turn signal needs to be switched hot. This is important for several different circuits. Most are switched, but the wiper, emergency flasher, brake light and light switch always hot. I'll try to remember to note which is which and why. Turn signals are switched hot because you don't want to accidentally leave them flashing and run down your battery when you turn off the truck..... duh.

On a sheet of paper put a big dot in the center and draw a very light vertical line thru the dot. This is for orientation where the cam on the switch is in neutral. [When you move the lever up or down, the vertical line will tilt to one side of the center dot or the other.... pull the lever down to make left hand contact, up for right like the real thing.]
Make the line about 4" long on each side of the dot.
The center dot is where the power in connects from the turn signal flasher to the turn signal switch. [A hot wire comes from the fuse block to the other terminal on the fasher.]

Draw a very dark heavy line on a right angle on the left side of the dot. This is the turn siganl switch lever.

Now put two dots across the top and bottom of your pan so that you can now draw an X thru the center dot. Put one dot on each leg (4 dots)
Notice that if you pull your lever down to make a left turn, the X will contact the upper left and lower right dots on the X.

The turn signal now contacts the left turn signal lights and these wires are the ones you connect to the individual bulbs in your light fixtures front and rear.
The bulbs are grounded and complete the circuit causing the lights to flash.
If you have any questions I'll try to answer them.

Again, wire each bulb separately.

Some of us have emergency flashers and I finally figured out how they work. I'll describe it and the light switch in another post.
U@ss

Uncle Skip · Post by **Uncle Skip** » August 29, 2009, 5:57 pm

Another explanation.
The original emergency flashers work wonderfully on our old trucks and I finally figured out how they work today.
(Note that I'm orienting the switch with the terminals facing the top of the truck. )
Draw a rectangle with a switch coming out of the bottom (of the page).
There are four terminals in the switch. Number them left to right in the "front" 3 and 1. In the rear left to right, 4 and 2.
Number 1 is where the hot wire (always hot) comes in from the flasher unit.
The flasher unit is connected directly to the fuse block hot terminal.
Number 2 goes to the dash light that shows the flasher is on.
Number 3 is spliced into two (and maybe three) wires as is the wire on terminal number 4.
# 3 is spliced individually into the left front and left rear turn signal wires. [If you use a third wire, it is spliced into the left turn signal indicator light in the dash cluster. But since you have the other indicator light, I'd leave the turn signal lights out of the harness.]
Number 4 is for the right turn signal wires and dash light.
Maybe now we're seeing why the original harness looks like spaghetti.
I'm wiring everything into plugs and splicing so that if I have to pull one circuit, I don't have to chop up everything in the harness.
I'm thinking that maybe some little two wire plugs from the junk yard would work on this application.
Is any of this making sense ???
U@ss

charliemccraney · Post by **charliemccraney** » August 29, 2009, 8:36 pm

Skip, does this help? It's based off of a 73-77 switch but it looks like it functions just the same, according to my '61 diagram.

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Johnny Canuck · Post by **Johnny Canuck** » August 29, 2009, 11:41 pm

wow. Took one quick 30 second run thru this thread and I have the beginning of a migrane already. Got to a spot where it said go get chebby parts from the junkyard and my brain switched to overload. Lord help me, some day I may have to read thru it all and live to tell the tale.
Godspeed Skip!

Uncle Skip · Post by **Uncle Skip** » August 30, 2009, 7:24 pm

Charley.
That nails it.
BTW, JC, a graduate of Canadian public school, and I think he only reads French.
I can't speak French, let alone write in it, so I've tried to explain in English the way it works for us in the lower 48, since most of us live here.
Hell, sometimes I think I can't even speak English after I talk to Alan......
ROTF
Seriously, once you understand the way it works, it really help diagnose problems.
Thanks for the diagram.

Thunderboy · Post by **Thunderboy** » August 31, 2009, 11:36 am

I'm enjoying this thread, Skip. Thanks for your generosity in sharing this. It is prompting me to seriously consider the "junkyard" approach instead of ponying up hundreds for a wiring kit.

Uncle Skip · Post by **Uncle Skip** » September 1, 2009, 6:05 pm

Guys.
It never got above 80 today so I spent the entire day working on the wire harness.
After thinking about it for a few weeks, I decided that the best way to wire the truck was break it down into components.
Lights - ignition - accessories. Each has its separate plugs and wire and each one goes from under the dash into the engine compartment where it will pick up and go to the required use with an individual plug and wire.

1.
I built the part of the harness for the lights in the rear of the truck. I can now unplug all the lights and lift the box off without having to take the lights out.

2.
I almost finished the under dash harness for the lights inside and outside the truck using the new light switch I described before. The harness is finished into the engine compartment.

3.
Completed the plug and harness from the instrument panel that goes into the main harness.
Now I can remove the insturment panel without having to deal with a lot of hanging wires. One plug, disconnect the speedometer cable and its out.

4.
Started on the thru firewall ignition components. Tach drive wires, starter wire, coil wire, fuel pump wire, horn etc.

I'll take some pictures tomorrow. I hope you'll be able to see the details and progress.
Its going to be a lot cleaner and usable with all those plugs letting me take out components.

Next I'll noodle the toggle switches and fuse box location.
Stay tuned.
U@ss

Alan Mclennan · Post by **Alan Mclennan** » September 2, 2009, 7:40 pm

Crikey!!!! I didn`t say nothing!

YET!

Uncle Skip · Post by **Uncle Skip** » September 3, 2009, 2:49 pm

Here is the harness that goes inside the truck.
Sorry, I couldn't get a close up of the gated toggle, but its the big one on the left side of the panel.
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U@ss

Uncle Skip · Post by **Uncle Skip** » October 3, 2009, 3:41 pm

Finished the basic harness and tested everything. Its pretty much ready to put in the truck. The plugs will be in the engine compartment and connect components inside the truck. Notice the turn signal plug that will splice into the wires coming out of the steering column for the turn signal switch.
I included a shot of the e-switch, rear lights harness for the bed, and the part of the harness that controls the starter, coil wire, ignition, fuel pump switch and gas gauge wire.
Makes a really neat and clean installation if you leave enough length for routing under the dash.
All junk yard parts including the wires. I had to buy connector/ splices and shrink tubing.
Cheap re-wire, don't you think?
U@ss
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jammck66 · Post by **jammck66** » November 12, 2009, 1:45 am

yup, my head definatly just blew up! lol