so ive been looking for months for a wiring harness for my 84 f150 L6. there is a local yard that has one for a manual. mine is an AOD. please for the love of god tell me that manual harness will work in my truck.

 

Being yours is a 84 300 six with AOD (dual tanks?) it would be a feed back system.
What part of your harness is bad?
If it is the feed back part this can be removed with a carb & dist change.

I cant say about manual / auto harness but I can tell you there is a difference between dual tank & non-dual tank harness for the 81 manual trucks.
On the 81's the AC harness is a add on so you dont have to find a harness that has AC for the truck, just swap the AC harness on to the non-AC harness you you now have AC if the truck has AC parts installed.

On my manual 81's trucks main harness that starts inside the truck and runs across the top of the dash going out the firewall on each side.
The right side (always sitting in the truck) in the engine bay has the wires for the starter / solenoid, head/park turn/side lights.
The ALT has a harness that plugs into this side of the main harness.

On the left side you have head/park turn/side lights, wiper washer pump power, wiper motor power, brake failure wire, a plug for the frame rail harness to the rear.
There are a few other wires by the booster but not a big deal ATM.

This frame rail harness will be different like the main harness if you have dual tanks or not.
It will have all the tail light wires (5 of them), wires for for tank sender(s) and the fuel switch valve, and to trans back up light switch.

Out back you have the tail light harness that would have 5 wires.
Pre 82? may only have 4 wires as the ground wire was not run in the harness on early trucks like my 81.

Now with that being said if the truck was a auto I think it would have a group of wires to the trans for back up lights and for the NSS so you can start in gear.
So my thinking there might be a good chance there would be a auto & manual harness besides dual tanks & non-dual tank.
If you have a AOD trans there is no computer for that trans so as long as the wires going to the auto are there you might be OK.
Guess you could count the number of wires in the plug from the main to the frame rail harness to see if the same number of wires are the same and maybe the colors?

I know not much help but if you give us a little more information on what you need to replace we may have a easy way to over come it.
Dave ----

 

I can verify on a 1989, that it's made up of different harnesses plugged together. I swapped my 89 from a c6 to a zf 5 speed transmission. I had a donor truck the same year right there at the house. After I swapped the trans in place, I found a plug under the brake booster that was the same on both the auto truck and the manual truck. I unplugged the auto harness, and plugged in the manual harness in my truck. It had a jumper made into the harness for the neutral safety and was just plug and play, no messing with any wires at all.

See if they were doing this in the early years also. I know they did with the different ignition systems in these years.

 

Yours sound like what AMC did on my 70 Javelins, auto had a harness that plugged in for the NSS & back up lights, manual only had a jumper for the NSS and a harness for the back up lights.

Being both of my trucks were manuals I dont even know where the NSS harness would have plugged in?
If I can think of it the next time I go through my parts bins and have the old harness out I will give it a quick look over.

Where would the NSS be on a auto trans, bottom of column or at the trans?
If at the trans then it may use a different frame rail harness as mine only has 2 wires for the back up light switch that is on the trans.
I also dont know if the main harness would have the wires for the NSS at the plug under the booster where the 2 meet up?
Remember the early trucks did not have a clutch safety switch so it would not have a jumper on the manual trucks if it was not a auto.
Dave ----

 

so i know the wire from the battery to the starter solenoid needs to be replaced. i follow the wires off that section of the truck to the firewall and most of them are cooked. and im assuming from the smoke that was rolling under the dash i may have some cooked wires there too

 

The NSS was on the side of the transmission on the automatics. I believe on most of the manual trucks, they used a switch on the clutch for the neutral safety circuit. From what I gather, the red/blue start wire leaves the ignition switch and runs to a plug on all trucks under the dash. Automatics got a jumper in this plug, manuals plugged into the clutch switch. I have never actually seen this jumper plug under the dash, but it is shown in the wiring diagrams and I have heard of a few people who have messed with it.

Once you leave the jumper plug/clutch switch area, the red/blue goes out to that plug under the brake booster.

From that booster plug on a automatic truck, the red/blue will continue on down to the neutral safety on the side of the transmission, and then leave there still red/blue, and go back up through that same plug under the booster, and then make it's way to the starter relay.

From that booster plug on a manual truck, the red blue enters the manual tranny harness, but it make and abrupt u-turn and comes back to the plug. In other words the manual trans harness has a jumper made into it's harness, and runs the start circuit right back into the plug under the booster. I have layed eyes on this on my 89.

 

That certainly sounds ugly. If you are planning on replacing the entire wiring harness, it's a pretty labour intensive job as the harness runs through the firewall in 2 locations and it's fastened to the dash way up high, so you pretty well have to remove the dash to replace the harness. The sections under the hood can be replaced individually, so if you can narrow down what needs to be replaced, it will help others to help you. The feeds connected to the solenoid at the battery cable post are on fusible links, so if you melted each and every one of them, there must have been a significant event to do that amount of damage.

 

Yea if the wires are crispy up to the fire wall and smoke inside it is harness replace.

If the harness you found is cheap enough and you been looking for a long time it might be best to get it as it is better than nothing.
Then pull the crispy one and lay them side by side so you can see just what is different between them.

That is what I did with my 81's and found that the main & rail harnesses were different between dual tanks and non-dual tanks.
I also seen the AC harness is a add on to any main harness.

My 81's do not have a clutch switch and why I was thinking there are 2 different harnesses, auto & manual.
Again I would have to pull out from the parts bin the other harness to see if there is the blue / red wire but I dont remember seeing a jumper on either harness.
Dave ----

 

Yes, I forgot about that. The early trucks didn't have the clutch switch. When did they start using one? 1983ish?

 

I think it was 1984, my 1981 has no such device (nor does it have a key-in-ignition buzzer).