Your white/black wire off the stator should go to the heater coil for the automatic choke on the carb.

 

The truck came with a manual choke carb and the wire was not wired up for this.

 

In that case the wire shouldn't hook up to anything.
The output of the stator terminal is ~7 volts AC not DC.

 

Wired as purchased.
Attached is my rough drawing of how things were wired up when I purchased the truck. Like I said this did not look like a backyard mechanics work and the work of a dealership or factory because of the factory style plugs and terminal ends. Without cutting the plug open or metering and seeing if those connections are actually in parallel or not, it could be that maybe it was a future proof thing in case someone wanted to switch to an electric choke and maybe you would just swap the plug right there?

 

You can jump across the two terminals of an ammeter as it's just measuring current quantity and direction through the circuit which it is in. It's not shorting. Say plus is towards the battery plus, and negative is towards the load . Jumping it just removes the ammeter like it was not there. When the load increases, like a bulb is turned on, the ammeter measures the amperage required for that load and shows it as a discharge as it's being withdrawn from the battery.

You can not jump across the two terminals of a volt meter as it measures current quality and then you are shorting the plus dc to the minus dc (ground on my '77). A dead short, a fuse blower, a "let the smoke out of the wire" action.

 

Appreciate the help, I've been a commercial electrician for over a decade so I have a slightly good understanding of HOW the magic pixies work. The thing is I never assume something does something the same way as if it were at work. Automotive electrical is a different ballgame and I take extra precaution when I don't have accurate specs for the circuits and devices.

I understand how an ammeter works its like a pressure gauge in a water main, my concern was the gauge had a + and - and thats when my eyebrow got raised, whatever factory made the gauge shouldn't have put the - on it but if you don't know then don't assume ya know?

I think I figured out a way to rewire everything to bypass the aftermarket ammeter. I will probably just keep the factory ammeter disconnected and do this rocketman swap I've read about.

Electricity is black magic.

 

The factory ammeter does not carry the full current, it's reading the voltage drop across a shunt in the alternator wiring harness. In effect, it is a remote mounted zero center millivolt meter which I think is one of the reasons they don't work well. The shunt isn't calibrated and a few millivolts may not be enough to deflect the needle on a 50 year old gauge. If any of the connections between the shunt and the meter have higher than designed resistance, the gauge won't read right if at all. The gauge is marked with polarity as it will read backward if connected backward, showing a discharge when the battery is being charged. No harm will be done, other than to your wallet and time if you try to trouble shoot using the gauge. Commercial shunts can be 50mV per full scale deflection, 75mV per full scale deflection or 100mV per full scale deflection. I've no idea what the factory gauge uses. For my ham radio power supply monitoring box, I chose a gauge that reads 30 amps full scale with 75mV applied with a shunt that develops 75mV at 30 amps.

In this snip from a '76 diagram, you can see that the ammeter is in parallel with wire # 38 "Black with red stripe" and that that section is labeled "SHUNT". If the alternator is working and charging the battery, the voltage at S-201 will be higher than that at S-202 by some amount and the gauge will deflect in the charge direction. If the alternator is not working, the voltage at S201 will be lower than that at S--202 and the gauge will deflect in the discharge direction. Measured at the gauge with a digital multi meter, you will see a positive voltage or a negative voltage based on this. On an aftermarket gauge with internal shunt, all of this happens inside the gauge and all of the current passes through the gauge. It may be that your original gauge is an aftermarket unit. If that is true, it should have been installed with heavy gauge wire and connected in place of the shunt between S-201 and S-202. Disconnecting an aftermarket gauge would be nearly the same as removing a battery cable. Some but not all of the truck will lose power, anything connected to the battery side of the starter relay will still have power, nothing else will. It's also dangerous as there may not be enough or any over current protection in that circuit and any short in either of those two wires will probably cause a meltdown.





Michael

 

The factory gauge in the dash was disconnected, YLW/BLK cut and hidden in harness with tape near the alt. They had an after market mount in a cluster under the dash, a fuse-able link in the chain, lots of branch circuits. I attempted to remove these aftermarket gauges a few months back and couldn't figure out why the truck wouldn't start after I did that until I re-installed the aftermarket ammeter. I thought at the time oh boy I'll re-engineer this later and just hooked it back up, I did increase the wire gauge from what looked like 10 or maybe 8 to a 6 gauge until I could figure out how to rewire and remove it. My goals were just getting everything up and running before I start re-engineering things. The aftermarket gauge is defiantly carrying the full current.

I live in a place where unfortunately I have a 3 day parking limit so keeping things running is critical. Also being harassed by security every time I pop that hood open.

The 654 circuit on mine is YLW/BLK and the 655 circuit on mine is RED/YLW.

 

Sounds like the PO left you a gift that keeps on giving. And it does put a damper on the festivities when working in a parking lot with security keeping an eye on you.

The aftermarket gauge explains why the truck wouldn't start, they put it in series with something like I mentioned above. Who knows where in the circuit though. If you can trace the wires back to the harness near the alternator, you should be able to just connect the two together to get rid of the gauge but that still leaves the added branch circuits. At least they protected it with a fusable link.

What year is your truck? I picked '76 for the diagram because you have a newer grill and headlight buckets than what's on my '74. Diagrams are here if you have need of them.

Michael

 

Its a 78, yes I've been chasing electrical problems since I bought it. I have replaced just about 95% of the electrical components at this point and I'm currently working on re-wiring the entire lighting circuit due to my light switch throwing sparks for some silly reason every time I turn the dimmer or it touches something metal. I had to re-wire a lot of the nonsense at the alternator, It was a cluster of branch circuits, plugs and fuse-able links, very green and corroded. Funny enough once I chopped that nonsense out the blinkers started working.

 

I also sent my original meter to Rocketman and had him rebuild it as well. Been in around 3 years now and works with no issues. Couldn’t have been easier.

 

Sounds like you're sorting this all out. But I had a couple of questions from earlier that I did not get a chance to ask.

Got a pic of this connector? Any chance the White w/black and the Blue are NOT connected to each other?

Because that's all that Ford ever used them for. I could be wrong, but I don't think we've come across a setup like yours before.
From roughly '73 on, we had electric chokes on all engine options as far as I know. Your truck would not have come with a manual choke from the factory, even with a six-cylinder engine I don't think.
With gauges it was just for the choke. With lights it was for sensing duties with the regulator.

Since it's a '78, I doubt that any engine came with a manual choke in your chassis. Can't think of one anyway. They disappeared as early as the late sixties in some models, and probably no later than the very early seventies in everything else other than the really heavy duty trucks.
So yours was an add-on most likely. Just like I did to my '71 Bronco.

Got a pic of the carburetor in question?

I think it was mentioned already, but those sound like the ammeter shunts for the original dash gauge. The gauge in your truck probably worked as poorly as in most of ours, so the PO probably just figured it was not needed and actually cut wires to prove their point. Maybe they thought that leaving it connected would interfere with the function of the new one?

​​​​​​​Since they go to the board on the instrument cluster, then without looking for any other circuits using those colors, it's a very good bet that they were indeed for the original ammeter.

I know you got most of that already. Just wanted to post up again to ask those couple of questions above. You added some helpful images in your first post, but we haven't seen any further pics of the parts and pieces you're asking about. The good with the ugly would be great. We know from what you're saying that it's kind of a mess in some areas, but we'd like to see those too.
Maybe "mess" isn't the best way to put it, since you say that it was very professionally done in some instances. But even those would be good to see.

Thanks

​​​​​​​paul

 

Thanks for checking back, I actually made a lot of progress today, today was connect the battery and see if I start a fire day.

Exterior lights are 100% rewired with new sockets, waterproof terminals, marine grade #10 wire, sockets bulbs, light housing assemblies cable supports etc.

I cut the factory ammeter cables out and coiled and staged them near fire wall for when I do the rocketman conversion at a later date.

I deceided to hell with it and removed the S wire (WHT/BLK) from the alt and removed it all the way up to the plug.

Deleted the aftermarket ammeter and rewired things.

Truck started and ran with no issues, all exterior lighting is working correctly now in all states, positions at full power. No half dim lights, blinkers work when headlight switch it pulled now.

Only electrical oddity that I'm probably gona have to start a new thread on is my master light switch keeps throwing sparks and my temp gauge maxes out when the key is turned to on position even without engine being started.

This wasn't the original engine to the truck and I think they were trying to build a racer. I far as I can tell it has the PGMR for starter, duraspark 2 for ignition, with gauges option, and slide in camper and trailer break wiring.

The carb that came with the engine was a rotten holley 4 barrel with a 460 performer intake. I swapped the holley for an edelbrock with an ASV2 with manual choke. The Holley had a manual choke as well that was missing when I bought the truck and really threw me for a spinner trying to figure out why the truck wouldn't start in the cold until the light bulb clicked.

There are a few other wires that are actually RED/YLW as well, I identified one of these today, master light switch to high beam switch, few more I haven't traced out behind dash.

I appreciate everyone's help trying to figure this AMMETER nonsense out and I think I have closed the case on this portion of the wiring. I may add a newer ammeter to the gauge cluster under the dash another day but I will wire it up in a much safer way than having all that current being pulled through the gauge like that.

 

The light switch has always been a problem on our trucks because the entire load of the headlights travels through it . What the rest of the automotive industry was doing at this time was adding relays to protect the circuits and hardware. There are many threads on how to do that conversion it's inexpensive and with your electrical background should be straight forward for you. Great work in getting this far.
If you haven't experienced the lights going dark at 60 mph your in for a treat. /s

 

I've actually experienced that problem on both my '86 F150 and '71 Mercury Monterey.

I've considered relays but generally my method of madness to try and get everything how it originally was before I go playing engineer, then I have a stable and known system to build off of.

Like the ammeter for example.