Hey guys, I'm getting extremely frustrated with the wiring in my 1979 f350 w/ a 460. When I got it. It has an aftermarket sound system from the 80s or 90s as well as a brake controller, and a trailer plug that was hacked into the harness poorly. I'm not sure what's been effected and what's still good but i had to buy a new cluster because the original was so brittle it broke from the simple pressure of my picking it up, and I also have a full mad ignition setup. I can't figure out for the life of me what wire to tap into for the msd switch wire, I've read into jsut having an external switch so idk if that's a good route. I kinda just need some guidance, I'm 16 and have have fought myself everything to the point that I'm at. I'm also wanting to just get rid of everything I don't need like the original ac wiring, all the stereo wiring, and the other non essential things like the old duraspark stuff. I know this seems like a lot so I apologize but it's just very overwhelming and I've looked at fordification wiring diagrams and I'm really just in need of some guidance.

 

Well break it down in problems to handle one at a time. Aftermarket sound system, aftermarket brake controller, trailer plug, MSD, old Duraspark wiring.

Just slow down a bit, and remember to tackle one problem at a time. Slowly take all the aftermarket stereo wiring out 1st, start tracing from the radio, amp, speakers ect... working your way towards where ever they tap into the trucks harness. Should be working towards ONE 2 wire green elec connector for the OEM stereo power. Actually BOTH sides of that plug are keyed hot, the OEM stereo get its ground from the chassis.

For the brake controller same thing, trace from the controller back to where it connects to the trucks harness and disconnect and heat shrink/cover/repair the splice in.

Trailer plug is on the back end tapped into the tail lights wiring harness right? Again start at the plug, trace one wire at a time and take it out of the OEM harness. Repair/splice the OEM harness back together. Not just with crimp butt connectors.

MSD is added in and aftermarket and I have NO experience, so I have no real good advice. Some might say ditch it and go back to OEM. That way you can trouble shoot it easier and get OEM parts from about any parts house.

Duraspark II is a reliable system and been around for quite a while. As far as the instrument cluster it is one piece and if you got a complete replacement, as long as you got the same set up, meaning either 4 gauges or 2 gauges and 2 warning lights (what ever you had before is what you need to put back in). It is plug and play, same plug for the new part.

The OEM stereo plug you are working back towards.

All my elec diagrams starts here. https://www.ford-trucks.com/forums/1...l#post14696846