I have a 1977 F150 with a 400 in it...doing a restoration project and needed to replace the wiring harness as the original one was butchered to death by the previous owner. I bought an E-Z Wire wiring harness because of a recommendation by a friend. So far, it hasn't been too bad, but the ignition/alternator pieces have me a little confused. Has anyone ever done this with E-Z wire? anyone have a better wiring diagram than the one that came with the harness?

 

You can also look up Painless wiring diagrams. One thing that helped me was the voltmeter so I could see exactly when I had power and at what stage(Acc, On or various switches). I had a whole EZ harness, but opted to use just a Painless fuse panel. It was easier to run individual circuits, but then again, I needed to have my truck running.

 

I recently installed the complete American Autowire harness. The main change is the harness is designed for a modern type alternator. That might be throwing you for a loop. Also, don't they have a tech support number? Without pictures of your issues or a description of the wires, it is difficult to help. Also, my harness was not designed to support the duraspark system, you may look into that as well. Don't panic if that is the case, there are work arounds, but I would start there.

 

Yeah, I got most of it figured out. I ended up using pieces of the old harness, which is fine. The one big thing is that the diagrams with the EZ wire harness indicates that the "alternator exciter" wire should be connected to terminal I on the voltage regulator. My voltage regulator either has never had a wire attached to terminal I, or something fell out of the factory plug as there is no connection post on the plug.

 

I didn't think that our system used the Exciter wire. I could be very wrong.

 

I didn't think so either, but the wiring diagram (as bad as it is) shows it being used. guess I'm gonna have to try and call them or try and look up a diagram from painless or someone else like that.

 

now would be a perfect time to do a 3G swap. I just rewired my truck as well, and did a 3G swap at the same time. only wires i had to hook back up were charge wire to the starter relay and green/red to the factory 2 prong plug that shares the horn trigger wire.

 

I am no professor of the wiring harnesses. But Could it be possible that the "I" was for an idiot light?