I have a 76 I need to completely re-wire. What years are compatible? I bought a 78 for this exact reason with all the option mine had, but the freakin wiring harness is different. What years WILL work? Or, will the 78 wiring work with modifications?

Oh yea, F-250.

 

I replaced the wiring from my 77 F100 with the entire harness from a 75 F100. There were a few differences, but nothing to serious. Had to use the 75 ignition switch, the 75 ignition module, brake light wire was in a different spot, and the front directionals were a different plug. I changed the entire harness and left the tail light wiring. Takes alittle time but better than chasing all the cut wires that were in my truck. Good luck.

 

I'm not completey sure but I wanna say the wiring is gonna be different. Mainly due to diferent options that the truck may have. I think the best be is to make one or find one off the same year and trim.

 

Well, I know the Haynes manual has the 75 and 76 wiring diagrams together. Every other year model has it's own diagram.

 

Here's the good news, I have both trucks, complete, sitting here. So, for issues like you had on the directional switch, I could just take the switch from the donor truck.

What has me worried, is the harness appears to plug into the drivers kick panel on the 78 whereas it does not on my 76. Anybody know what that plug is and why it is there?

 

That is exactly what I did. I had both trucks and took what i needed. There was a green plastic plug into the drivers side frame that I believe was for seat belt buzzer. The 77 had it and the 75 did not. I removed it and no issues. Didn't really plug into the side, more of a push in pin.