Electrical confusion and mayhem

Time for my first question! My 84 is quite the electrical nightmare. It came back to me with an Edelbrock carb and a gm style HEI distributor. The crazy engine harness and brain box were in the bed of the truck and I've deduced that I need absolutely none of that mess, (Likely for sale if anyone needs it). Also, the original body wiring harness was supposedly bad so anouther harness was put in the truck from an unknown parts truck and additional parts of harnesses were in the bed of the truck.
I'm stubborn and i want to get this puzzle figured out even if it takes a few months off of my life expectancy!!
I've already got the distributor, oil, and coolant temp wires located and spliced into their correct locations. Truck starts with the key and runs good, which is a huge step from the alligator clips and screwdriver condition it was in last week!
I'm pretty sure that the body and chassis harnesses don't match due to some of the connectors not matching.

I printed off the 1985 wiring harness and have strained my eyes for hours and it's helped a ton, but there are a few plug-ins that I just can't find. Guessing because my truck is an 84 🤪

So for me to attempt to figure out as much of this as I can without blowing up this forum, or paying one of y'all to come visit...
Are the wiring colors fairly consistent for all of the years of our bullnose trucks??
A good example would be the body to chassis plugs on the driverside fender apron. The light plug matches and fits. BUT, the second chassis plug which includes the fuel Guage wire is a 4 plug with 2 used pins, while the body plug is an 8 plug with all 8 used. Not sure what the extra wires go to except maybe to the dual tank solenoid??
I assume it's safe to say that the similar colored wires (black and yellow if I remember correctly) could be connected and complete the chassis/body connection?
Knowing if the wire colors are consistent would greatly help when I can't match the plugs either on the papers or on the truck.

I apologize that I made y'all read so much into that, I'll try to make my next correspondence a bit shorter!!! 😆

Help me help you.
I have NO idea where you are..
My rear axle in in a zillion pieces.
But I can read a schematic, and know these trucks.

Show some pictures of your questions.
Make it big enough that I recognize exactly what you mean.

TrevD wrote

Are the wiring colors fairly consistent for all of the years of our bullnose trucks??

I have a 84 too.  And I use the 85 wiring diagram, it matches.

As Jim suggested, you should go step by step and send a picture of each part of harness or connector you are trying to elucidate.

One by one would be great and more easy for helping you.  Pretty sure that people here can help you to untangle this spaghetti.

The wire colors are VERY consistent.  In fact, if you go to Documentation/Electrical/Standard Wire & Color Codes you'll see the colors, circuit numbers, and applications.

There is a minor glitch in the 1985/86 timeframe.  The 1986 EVTM states that for that year and after the dots and hash marks previously used in addition to stripes changed over to all stripes.  But it didn't happen on the stroke of midnight on December 31st.  Big Blue, an 85 with a build date of May 85, has some of the striped wire harnesses that supposedly should have been hashed.

As for staring at wiring diagrams, don't.  Use the EVTMS.  They break things down into systems and lay out the wiring for that system on one or two pages.  Plus they have notes as to where components are located and how to troubleshoot the system.

I'll note that on my 1984 (build date of 12/1983 in Oakville, ON, also a 300) I've also found striped wiring along with dotted wiring. But never mixed in the same harness.

Prior to the change they used stripes, hash marks, and dots, and the EVTM shows which wires should have what.  But Big Blue has stripped wires where they should be hashed or dotted according to the 85 EVTM.  It isn't a problem and the wiring colors are the same, but you just have to realize that the book isn't exactly right for every truck on all those details.

Ok, I understand.
One by one on individual topics or just on this topic? I don't want to get in trouble for loading up the main page 🤣

If this topic is "electrical confusion and mayhem," then post all your electrical problems here.

Ok, I'm going to try my best to load up some pictures.

I do want to start off saying that I don't know if the truck originally had duel tanks. I haven't found the pictures my dad took of it when he drug it home, but it had duel tanks when he was done. the duel tanks were ran off of a toggle switch on the dash. that and the chassis harness doesn't appear to support the duel tank setup and i strongly suspect my dad just made it duel tank.

The person that got the truck and tore into a couple of years ago put in a dash/body harness out of an unknown ford truck that I'm suspecting had duel tanks. There are extra wires, and the ac control unit that came with the spare parts has the tank switch in it.








First, the above plug is currently sticking out of the glovebox but wire memory makes me think it was close to the fuel tank selector, though its the wrong plug... and I cant find this plug shape anywhere. It has a couple wires in common with the next plug situation I have.



the above picture are of the body side of the harness under the brake booster, the 2 purple wires are common with the aforementioned plug hanging out of the dash. It also has 2 wires, the small black and small yellow wires in common with the chassis plug that's shown below. I know that the chassis side black and yellow are ground and fuel gage. im sure yall know that already, im just still getting excited every time i figure out where a wire goes  







Before I cut into it and just splice the black and yellow together, I want to make sure all of my thoughts are correct. If all of the above is true, i would like to keep the option available to add my own extra wires to the back to support the second tank in the future. but since only 1 tank has been replaced and the wiring doesn't match up, i just want to get the current set up to work and be drivable. ill fill in the blanks later!

Look here:  https://www.garysgaragemahal.com/1985-evtm.html

I promise I'm trying but I can't find that first connection. It's in the area of the radio, clock, ash tray, ac controls and fuel tank switch. But I can't find that plug and none of the colors match.
I know I'm going to feel stupid when it's Pointed out to me, likely in plain sight.

As you read the EVTM that Jim shared, pay close attention to things like DG/Y, R/W, that means the wire has 2 colors. For example, DG/Y means the wire is Dark Green but has a Yellow accent like a stripe/dash/dots. The EVTM also has good illustrations on the accent shapes. The reason this is important is because there are so many Red wires for example, and if you also pay attention to the secondary accent/color/shape it makes it pretty much certain in deducing what is what.

My first Bullnose was a puzzle I had to work out, once you get the hang of it, it is easy. The good news is once you know a Bullnose, the others are very similar.

Good luck hunting down those wires!

Yea, I know the color designations and USUALLY fine wiring diagrams and such quite enjoyable... in a weird and twisted way 🤣.

And yes, the electrical manual that's on this site is layed out in a very impressive way.
Both the 85 wiring harness and the EVTM have helped me immensely in the past 2 weeks get a LOT done with the birds nest that I received when I got the truck back.
The cab was completely stripped with no dash, heater box, wiring harness... nothing. This site has gotten me from nothing a week ago and now it starts and runs and doesn't drain the battery.

I get that. It is very satisfying to find those wires on these old trucks and realizing "Ok one more wire that hasn't been monkeyed with before"

Buy yourself a copy of the EVTM. Nothing like a hard copy on hand.

https://www.ebay.com/itm/273763121144?itmmeta=01HR0WVQVFDYB68CZSR68WTERR&hash=item3fbd8db7f8:g:sF4AAOSwRv5k3gFy&itmprp=enc%3AAQAIAAAAwMvXQFpwK9D%2BsMwrmII0eCIpR3YIQqSxwkJBUV%2FxytCt%2Fz2Yt%2BiG%2BiKssa%2FXbV0bPFPHcxMXx5Wy%2BkDOpnZfExVgFpOVwoarkC0NXWtONSbAT5vVPkvQyjoP6tFn4Ydj%2B2yMgqPAb%2FUQApaa%2B4SnV0EDmCZJBz0PKmWF8QeRZpwXhpquwqcaBUc%2FzBKg%2FP24cClmGILXWbDpEvfOwS4g%2FK4psFqMFVkxUNi0VUXfff%2FRzgX3S%2B6wxLwMmle%2BvDXnkw%3D%3D%7Ctkp%3ABk9SR-z97pzAYw

The only 3+2 pins connector I find:


is this one (C-402):


But wires colors nor form match.

Exactly!!! That's 50% of my headache!
I can't find the physically present plug in on paper yet

If the wire colors were similar, I'd just assume that the switch or plug changed at some point between 80 and 86... and I'd just find a way to wire it accordingly. But I'm at a loss so far.

When I get home I might just go back to the 85 wiring diagrams that I printed off and start looking for the wire color and track it that way 🤷‍♂️

One thing to note, in the EVTM only the circuit you're investigating is shown.

Connector 'C123' may have R/O/Y on the fuel pump circuit, and on a totally different page 'C123' may reappear with G/B/P on the tail light circuit.
Both are C123, but 123 is a six wire connector with two distinct circuits running through it....

Jeff is good to point out that the connector bodies are also shown.

I've looked over every page of the regular wiring harness as well as every page of the EV manual. I can not for the life of me find the part of the harness in question. to share the pain, i ever took the printed papers over to my moms house to see if she can find a purple wire with either a light blue solid tracer or one with a light green solid tracer.

the connection under the brake booster, C121 fits together and all matches... no problem there.

the other connection that's supposed to be there is either C124 or C127... and that's where I'm lost.

the chassis side looks to be C124, small grey connector with yellow/white and black wire, perfect.

however, I still haven't positively identified the body side of the connector, due to most of the wire colors not matching anywhere that I can find. Not to mention that the body side of the connection is black and not grey.

I'm really hoping some one can help me figure out what these other wires are for as this will also solve the mystery plug in the middle of the dash.



if im not mistaken, the above is C121 which matches and attaches as it should.



this little grey plug with the y/w and b wires is for the fuel gauge, that part makes sense.



this plug though doesn't match much of anything except for the y/w and the b wires. I cant find any of the other wires. I thought MAYBE it was dual tank... but none of the remaining wires match anything on the wiring diagrams or the EV pages.

I'm beyond tempted to offer a gift card or money order as reward for helping me get past this!

All of these are in the 85 EVTM:

There's a P/LB wire on Page 27  running from the ignition module to the distributor.  And on Pg 141 going from the speed control amplifier to the speed control server

There's a P/LG wire on Pg 123 going from the driver's tailgate window switch to the tailgate window switch on a Bronco.

C124 is shown on pages 5, 10, 21, 63, 70, 73, 80, 81, 82, 98, 103, 123, & 124

C127 is shown on pages 6, 7, 10, 14, 98, 99, 102, 104, 105, 106, 110, 116, & 134.

Hope that helps.