Hey yall i have a 1979 f150 i picked up 4x4 and someone had already cut the harness out planning to do a cheap eBay harness so i dont have much of the original left. But it has different plugs from any harness i have seen for the rear lights harness that comes from the firewall to the back of the truck. I have 4 of these trucks and pulled the harness out of a 79’ 250 and a 78’ supercab and bought a third off eBay and none of the plugs are made to connect to the rear frame harness that’s already in the truck. What do i need to look for?
I’ve went through a lot of diagrams and haven’t found anything that looks like these connectors fordification being the main area.

#ad

 

Mtdentside, Welcome to FTZ!

So the wire's from these 3 connectors into 1 taped harness goes to the rear of the truck, for stop(signal), tail, back up lights and the fuel tank sender(s) if 2 tanks, neutral safety switch if Auto transmission?? YES?? Did the cut ends go thru a grommet on the firewall where they would have gone to their points of hookup and someone nipped them under the dash?? You looked under the dash for the corresponding nipped wires?? Is this a cab swap you aquired??

Questions Yes and no answers for you now, we need a better understanding of what your dealing with.

Cap

 

Hey iicap thanks for the reply. Yes for the wires going to those locations. No for them going through the firewall as they aren’t long enough and no extra holes available. No to the cab swap as it’s all original and complete truck minus dash and engine harness.

all the other harnesses i have for similar model years and trucks had green connectors for the frame harness and this is the only one I’ve found that had this style with 3 connectors.

 

Another question, is your truck a trailer special? I have a '79 TS parts truck, and I think it has that square plug, left side in your picture. It is 30 miles away and the wiring is bad, but I should be able to look closer in a few days.

 

That would make sense if it is. I’d have to get underneath it and check for brake controller and what not. Would you be willing to part with the wiring harness? I’d love to make this thing back all original

 

The wiring may be cut up, I have to inspect before I say. Look for a relay on the firewall or inner fender, near the booster, or some holes were the relay used to be. Also look for a badge on the tailgate, if it's original. The TS did not have a brake controller from factory.

 

I didnt notice a badge on the tailgate. The po said that someone had fixed it up for their kid years ago so it could have been removed while painting. I will look for the relay but the po also removed majority of the electrical system off the firewall side before i saved her. I have remnants of the dash side but it’s all matching to the standard harness. When i saw the 3 plugs i figured something was up and it was a special optioned truck of some sort.

 

It is very common for tailgates to be replaced, so that is not really going to prove anything, really. Just look for some empty mounting holes, there were 6 small divots, 3 sets of 2, stamped into the fender, I think. Only if the option was installed, were the holes made.
Also, check for the trailer plug at the left rear, behind the bumper, and look for a plug between the cab and box, used for the optional camper shell (canopy).

 

Awesome. Thanks so much for the info!! I thought the camper and trailer specials were just for the 250s and up but after reading on them i see they had the 150s. I’m so hoping your wiring is intact. I did notice some holes that just looked kind of out of place of where anything would mount on the fender when i was looking at the wiring earlier but i could be wrong

 

It is possible that harness was used for any truck ordered with the topper, so it may not be exclusive to CS/TS.
A friend of mine has a '77 F150 TS, I think CS was only F250 and SCS was only F350, however that changed over time, bumps were available with the CS package on F100s.

 

I have the harness out of a 79 250 cs and it’s the standard style with the green and gray connectors

 

Have you or would running the VIN give you specifics, possibly Dealer Specified Options (DSO)

Cap

 

I had a chance to look at my trucks today, the '79 TS has the green plug. I also have a '79 F150 4X4 SCab with the same, but an identical '78 with the 3 plugs in your picture. I have 2 '77s with the 3 plug set up, and a '73 that is similar, but not identical. I am thinking either a running change was made in early '79, or your truck is a '78.

 

Sask thanks for looking. This wiring is so confusing haha. It’s weird because i also have a 77 150 that has the standard green plugs. Any of the 78 or 77 harnesses you would part with preferably ones that had ac

 

It would have to be like a marti report to get any of that info but yes i did decode the vin but it only tells so much