Converted truck from 2G to 3G and now 1G, how do I get this ammeter to work?

Years ago, I converted my 2G alternator to a 3G, worked great but I have had horribly short alternator belt life and squealing on startup ever since even with a way larger than stock alt pulley (single V belt) and I don't have any high amp load on the truck so I said to heck with that and converted it to a 1G system. The ammeter worked great with the stock 2G but it never has worked with the 3G other than showing a discharge with everything on even though it was charging. I know it's capable of working because I accidentally hooked one of the ammeter wires to the voltage regulator and it was doing some sort of exorcism type of movement in the dash until I fixed that. I've looked at some factory wiring diagrams and it's confusing as all get out since I'm looking at a 2G wiring diagram with now a 1G alternator setup. The 1G works great, but the ammeter does nothing. I removed all of the stock 2G wiring up to the 4 pin connector on the fender that contains the power wire going into the cab along with the ammeter wires. Everything that was hooked to power is still hooked to power but at my megafuse/junction block. Are one of the ammeter wires supposed to hook to the alternator side of the charging system and one side to the battery side? picture of how it's wired for reference. All of the wires do go to the battery side of the megafuse in case that pops I don't lose power to the inside of the cab, but it doesn't look that way how I have it routed under the cover. The large charge cable and megafuse are leftover from the 3G swap and I just decided to reuse it.

You're missing a few things.
1) Red/Orange is the other side of the ammeter. It needs to be tied to the battery side of a shunt wire.

2) The alternator can directly power the cab main power (yellow) and the ammeter (Y/LtGr) but you need an impedance (Shunt, shown as Bk/O between S202 & S203 ) for the ammeter to be able to react one way or the other.

3) The LG/R wire (904) is stator 'excite'. It should go directly to the voltage regulator from C610, not to any kind of power.

I think you did only one thing from the recommended 3G upgrade shown below, and that is to move the alternator's output to the starter relay, as shown with New Charge Cable.  But you didn't disconnect the Y/LG wire as shown, so the ammeter worked - in discharge only.

Now you need to put things back.  But I can't tell for sure what wires you have where from your pictures.  So you need to take more pics and show where all of the wires from that connector, C610, go.  Specifically the R/O and Y/LG.

Jim - You beat me.  I got started on a response and then my son called - ill.  So we've been re-planning our trip.

He needs to lose the beefy charge cable coming from the Megafuse and go back with a shunt that has some resistance.
The R/O wire needs to go to the battery end of the shunt. The ammeter won't budge if both sides have the same potential.
The 'large cable' is not going to show any drop. It needs equal resistance to the Y/Lg - R/O loop through the ammeter.
The Lg/R alternator 'excite' wire was never connected to power (except through key in run)

Look above...

FordFETruck wrote

the 4 pin connector on the fender that contains the power wire going into the cab along with the ammeter wires. Everything that was hooked to power is still hooked to power but at my megafuse/junction block. Are one of the ammeter wires supposed to hook to the alternator side of the charging system and one side to the battery side? picture of how it's wired for reference. All of the wires do go to the battery side of the megafuse in case that pops I don't lose power to the inside of the cab, but it doesn't look that way how I have it routed under the cover. The large charge cable and megafuse are leftover from the 3G swap and I just decided to reuse it.

You are right.  I got sidetracked by my son's call and didn't look it over well enough before responding.  

I'll bow out and let you take it from here as I'm still working through the implications of him not coming in tomorrow and us going on the trip.

Sorry to hear that.

I know how much you were looking forward to that adventure
Hopefully he's better soon and things work out.  

Yes, I was really looking forward to it.  But he is really, really ill and he couldn't enjoy the time, so we are rethinking.  More later.

Ok sounds like I have some rewiring to do. The key on 12v Indicator light (green wire hidden under the loom) is hooked to the S terminal on the regulator like some instructions I found said to wire it. Stator is just hooked to the electric choke, A on the regulator is the one wire coming from the fender to megafuse in its own loom for 12+ reference to regulator, I on reg is not used with ammeter, F goes to field terminal. Ground wire from alt to reg body is in place. The small red wire hooked to the megafuse has to be hooked to 12V otherwise system would not charge, same with the small yellow or green wire, I forget which one but it wouldn't charge without that one hooked to battery either. Where do I get a shunt wire and what size is needed? One wire also always has been hooked to the starter solenoid on batt side, the little red with silver/white tracer barely visible.

Sorry, I should have said Lg/R to the 'S' terminal of the regulator.
Yes, the regulator is wired a little different with an ammeter. That's why I included the illustration from the EVTM.

I need to get my glasses because I only really see C610* and that single 'A' hooked to the always hot Megafuse.
(small red, small yellow, small red w/silver or white I know nothing about)

The R/O coming back from the ammeter and your 'A' wire should go to the constant hot (battery+) lug of the starter relay once you replace that cable from the Megafuse to the lug with a shunt.
Unfortunately my Ford buddy passed over Christmas, so I can't just pop over there and rifle through his garage, find a shunt and ohm out for you.

I tore the original wiring apart looking for a shunt when I did the job but I'll be darned if I could find it. Only thing I found was like two joints of some wires soldered together in different areas of the wiring harness going to the alternator. I don't think I tossed any of that yet so I guess I should look at it again.

Well, the shunt is just the original length of B/O charge cable between the splices, as you see in the EVTM image.
But if you went and changed a bunch of the harness I can't say what that value should be.

I need to figure out what these other three wires that you have hooked up are.

Yeah, might not be easy or worthwhile to make it work at this point If I can't figure out the shunt value. I have an aftermarket volt gauge in the truck so I'm not unaware of the state of charge at any time either way, but t would be nice for it to work since it's the only item on the truck that does not function.

It sure would be nice if it worked!

Essentially the fused side of your HMEG becomes S202...

You need the 30" or so of 10Ga that represents the B/O shunt and move the regulator 'D' and the R/O ammeter return coming from that C610 all over to the hot starter relay lug.