One of the wires going to the connection on the side where there is 4 wires is also red and green and had around 12v so I decided to cut that wire and splice it on the other side of the connection to the other red and green wire just to try and get 12 v to the alt to see if that’s the problem. So I cut the wire, tested it after I cut it and it was still reading around 12 volts then the second I connected it to the green/red wire on the other side of the connection it dropped to 3.3, I have no idea, any ideas?

 

The Light Green/Red wire starts at the ignition switch. Near there is a splice that feeds a few different circuits including the alternator exciter circuit. If you have multiple wires spliced in the engine compartment as you state, I would suspect someone before you has modified the factory wiring. Again, this is where a Ford EVTM manual comes in very handy. From this side of the internet I can only speculate what you are seeing and trying to redo.

 

Ok I don’t really have one of those manuals but I’ll take a picture of the connection but what would cause a wire to have 12 v then when it gets connected to another wire for that to change to 3 v?

 

Corrosion. Loose crimp. Crushed wire with maybe one strand trying to flow the power. Who knows.

There is a connector about 3" long total under hood with the green/black. Unplug it and see if you can just make a jumper from the battery to the alt side of the green/back. If it charges, work your way back in the body harness.

 

It never hurts to have the same information the Ford techs used. If not for now then for the future.

 

ok I’ll try that when I’m home tonight

 

yes I’ll look into getting something like this for the future

 

There is some relevant charge circuit info here (based on a 1986 model year truck): https://www.garysgaragemahal.com/cha...e-engines.html

 

I will grab you a pic from my '88 in a few hours of that connection point. It may help.

 

Thank you guys

 

So taking a break from this one, got another truck with electrical issues, thank you guys for helping.

 

Forgot pic of plug, sorry!

 

No worries, that’s weird I have the same one but I have 4 wires on the one side and just the one on the other

 

That plug with your thumb on it looks like the processor ground wire

 

The connector only has that, I did a 3G swap probably 20 years ago so honestly cannot recall how the stock harness appeared. 100% that is the switched wire. I do seem to recall it was two pieces in one loom.

It is green/red. I swore green/black. Wrongo!

The PCM ground I have in pic below. I flipped my cables to match the 1992+ style as my batt hold down failed once and positive arced into the fender. Fun. I just run a 92+ positive cable anyway as I have a PMGR starter and my ground is the good, used from my '96 7.3.

Bunch of stuff out as cleaning and changing stuff up