I am still figuring out the multimeter too I really am a hot mess LOL!

So, just like I checked my voltage regulator, just check alternator battery stud to ground and it should have infinite resistance, is this correct?

DONT check batt positive to ground with an Ohmmeter!!! You'll fry meter or blow it's fuse.

Voltage Regulator.
Here's how it works.
Inside the alternator there is an electo-magnet which creates a Field.
The voltage regulator controls the power going to the electro-magnet. If you look at the '67 Charge Circuit, you'll see just one wire from the Voltage regulator power to the Field. The circuit is completed by the negative grounded to the alternator body. This style voltage regulator controls power on the hot side.

Now take the '67 diagram and remove the field's negative connection to ground. Instead run a wire to the Voltage regulator. This is what your Voltage Regulator is controlling. It's comparing the voltage at the ignition wire, but controlling the ground.

The Alternator
Current is induced by the spinning magnets. It flows out when there is a lower voltage anyplace the alternator's output wire may be attached to. It should not be in contact with ground except through operating equipment.

I think that's all correct.

There is no battery connected currently. That is something stupid I would probably do though....

Yes. That is correct!
PacNorth is correct that Ohmeters can not be used on a hot circuit. However your charge circuit seems rather disconnected! But yes, your best with the battery disconnected.

If you later want to check for voltage drop, that gets done on a hot circuit. The 1948 and '53 Master Tech booklets explain how to do volatge drop tests.

And as far as a mess, I dunno about that. Slow down if you need. Take notes, even if you toss 'em later, for most of us they help with this complicated stuff. For wiring, my notes are usually drawings. The messy versions I don't post, even when I keep 'em.

Ok, so just to recap for the day before I take a break from all this.

-I checked for continuity on the engine side of the wire harness.

-I did find a small gauge fried tachometer wire that ran to the ignition coil. That tachometer and wire was eliminated.

-Checked the voltage regulator (which I assume is bad) possible cause of problem?

-Electronic ignition module wire that connects to distributor has continuity, probably a ground.

So for my next step, connect all the wires so I can check for ground to short? If I understand correctly, the wires have to be all connected in order to check that.

*Without simply connecting the battery and seeing what wire fries first, of course

so I guess either check works. multimeter or test light.

multimeter doesn't need the battery connected. So it might be safer.

they way I described gives you an instant read instead of having to look at the meter. so I prefer it as faster to check circuits.

you should get a light at the alt case, but not the big stud on the back.

unless it is grounded. then I would pull the alt and have it tested as well.

if you follow the circuit path, you have power at the test light to power. It would be like touching it back to the pos terminal on the battery. nothing should happen.
IF it lights, then you have a path back to ground.

In some cases, that might be correct, like I don't know about the 2 field vr or the electronic ignition.

in others this should not happen.

The relay stud that normally connects to the battery should not light up. again like touching the end of the test light back to the pos of the battery. it shouldn't complete the circuit.

if you pull all the wiring from the relay I would check each one to find which one causes it to light up.

my way you don't really need to plug it all back into the bulkhead. Just make sure the ends are connected to whatever they go to. touch each wire in the connector and see if it lights.
if it does trace it or disconnect the end and see if it still lights.
if it does the wire has a break in it and it is going to ground.
if it stops lighting, then check whatever was at the other end to see if it is supposed to be grounded.

Damn! Too lazy at this moment to read with datail every post LOL,

Think on this. EVERY device in car is indeed a controlled and potential short. A Bulb is a short, a regulator is also somehow a short etc, just at diff values what makes them more a Long than a Short LOL (j/k)... don't check the devices going to ground. The short you got is a direct wire to ground short. By the wires affected, you only could get a short on red and black wires or related items... this means, black wire between alt and bulkhead or alt stud, red wire between starter relay and bulkhead or starter relay stud, red and black wires between bulkhead and ammeter... or even Ammeter itself with cluster housing.

Any other short around will burnt that wire first.

A short like that where the big gauge wires where affected and none else, it means was a straight short to them. If none other wire was affected, then you didn't have a short anywhere but on those. A short on another wire was give you a burnt sign way before these two red and black. You got the short straight in there.

I'm agreed with has being posted about the short should come somewhere between ammeter and alternator because if it was between amm and fuse link, the black wire was never burnt.

Aside that, all those devices are just energized with key in RUN, but not straight from batt. The short came into the batt source network.

There is a chance the short is now gone with all the wiring movement.

For your peace... it is on that way. Is a good signal the ECU is good. One of the pins of ECU is straight to ground and matches that wire, so with a test light, the light will light on

And I'm positivelly toward to this.... the black ammeter wire was already damaged close to bulkhead on cab side, due the tipical mopar overheat fail over a poor iddle capacity alt. This overheat melted the wire cover allong the years until get it naked and SOMEHOW this naked wire section grounded around with anything on cab just right now... and this was the final result.

I wouldn't overthink more this. That's my conclusion.

The melted engine harness plug looks old enough to get this conclusion, not a fresh melt. The short was the next fail after this melt

Fix the wiring, get a better output alt and you are done.

Set the new wiring out of the bulkhead straight to amm studs through the firewall with a grommet, and replace the amm-splice path with a new wire. Forget about the splice to bulkhead wire section. The amm stud will become on a power junction... just need to be clean and tight.

You can use this kind of plugs ( picture attached ) to be able to disconect the main wires on engine side. Cut a long piece to reach the ammeter to engine bay side keeping the plug on engine bay side , and the short piece plug to splice in there the new engine side wires...

These quick disconect links are available on 10 and even 8 gauge wire, from 12" up to 24", 48" long. There are several vendors around and several setups you can match your needs, some are already cut to be spliced.

The pictured wire is the one ( in hands now ) I will be mostly sure using. 10 gauge I think 48". At this moment I don't have quick disconect plugs at this moment in my setup which I hate. i like the stock versatility to disconect everything, so this will be my next upgrade. Mostly sure will be eliminating also the stock engine bay side wires from starter relay and alt, but will keep in place the underdash wires section ( in my case no need to remove those actually ), or maybe just will remove the red wire betwen bulkhead and starter relay just to make easier the fuse link splice using just one 14 gauge fuse link, instead one fuse link for each wire, the parallel path amd the stock one. Two parallel fuse link can take FOREVER to burn in a short

Also have a 8 gauge I think 24" but not sure if 24" will reach the ammeter from the engine bay side. Couldn't find 8 gauge 48" quick link harness

Yes. Agreed. This the other scenario. Without checking as we have suggested, the truth will be unknown. Can't really help any more at this point. All the information to solve the mystery and prevent future problems is here or in the links. It may take a a few rereads and some homework, but its all there.

Just edited a bit my last reply, about the wire I will be using in my own car

Good detective work there Nacho, that is a very good likelyhood, that it full fielded or near FF'd, enough to melt the insulation in that main circuit then it dead shorted. Now that I think about it when my '66 dart full fielded for awhile the insulation was badly shriveled & I did not notice a problem till I popped the hood later for something else & saw the carnage. I musta missed the ammeter reading. It ran fine & did not dead short but it didn't seem too far from it from the looks of things.

just found this to make your own design and custom wires... IF you don't want to make them by yourself whcih is way cheaper as far yo0u get the toolings and materials

https://powerwerx.com/single-conductor-custom-cable

also dual

https://powerwerx.com/dual-conductor-custom-cable

you can make a new fresh wiring between alt and batt going through the ammeter with quick disconect wires in the middle meeting your needs.

separated wires

1/4" eyelet for ammeter ends

3 feets lenght 10 gauge, one red one black.

Black wire with 75 amps powerpole end
the red one with 45 powerpole end

one extra 45 amps powepole end and 3/8" eyelet terminal for the new 14 gauge fuse link

alt black wire with 75 amps powerpole end, 5 or 6 feet ( which ever the lenght is the engine bay need for the alt, I don't have the measure ) wire and 3/8" eyelet terminal

grommet on firewall...

done.



just an idea

and of course A GOOD ALT!!!! if money is not a problem Tuff stuff 100 amps alt is my sugestion which is my dreamed alt ( which I can't afford by now )

EDITING ONCE MORE...

also the 1/4" eyelet terminal and bare end, maybe 1 feet long or a bit more, black wire ( 12 gauge is enough like factory ) to feed the factory splice into the underdash harness

and forgot you got a 71, where the starter relay is at a side of the batt... so will need the powerpole end extension to reach from firewall up to fuse link ( maybe 4 feet long ? )... or get the amm/starter relay section that long instead getting a powerpole plug leaving the firewall... maybe 6 feet long ?

Great work guys. Hopefully this works for him.
So what will the ammeter show if it is starting to develop this issue? My battery shows normal voltage when running (between 13.7-14 V), but the ammeter rises far to the "plus" side on acceleration no matter how long the car is running.

p d'ro ( what kind of nickname is that ? LOL )

read the link about alt and wiring upgrades I posted first, or Mattax links which also takes to my thread about, with more information from him

have you got some extra accesory being sourced straight from batt ? thats a big NO when you got ammeter. The charging reading can be due is sourcing the extra devides on batt pole and not really charging. That add strees on wiring and bulkhead terminals. EVERYTHING must be feeded from the alt side when you got an ammeter on a car

Mostly what I did was some editing of the English and diagrams.
P d'ro, Read the explanation and you should be able to figure out where the problem is. If you have questions, maybe start a new thread; we're happy to help. Understanding the Charge Circuit

yeap, well... my english just need to get better LOL

Will do guys. Not sure about the terminal draw. Will check.
I have been following this thread closely as I do have a new engine harness, but an original alternator and ammeter so the tips on proper crimping and the wiring bypass are excellent.
To the op, are you going to keep your ammeter or bypass and go with a voltmeter?
How hard was it to clean your bulkhead terminals with the doexit? Was it difficult to pull of the cowl bulkhead connection? I am afraid to torque on mine as it seems fragile.
Keep us up to date here as we are all interested. Can't wait until you ID this short.
I actually will use these crimping tools to update my original '70 Bronco wiring.