grego, by no "key switch" I mean the whole switch with the key hole has been disconnected from the harness with all the wires that fed into it (as far as I know, that's the ignition switch). I've been going through, pulling all the tape wrapping up wire bundles to try to find something I can visually see is wrong, nothing so far. Believe me, at this point I'm VERY aware the alt shouldn't be getting power with the ignition switch with the key in the off (or the switch removed completely).

danlee, I'm sorry, but you'll have to dumb that down to my level... As I've stated before, I'm a complete idiot when it comes to auto electrical. I have little to no understanding what all that means...
I understood "hot wire," "keyswitch" and "voltage", that's about it.

 

When the keyswitch is turned 'ON', battery voltage is supplied to the + terminal of the coil through a resistor or resistor wire, and also to the field of the alternator through the voltage regulator, and other places as well.

When the keyswitch is turned 'OFF', there is no voltage applied to any of these places.

If the keyswitch is 'OFF' or disconnected, and voltage is being applied to these places, it is because a 'hotwire' has melted insulation and is in contact with these circuits through melted insulation. If you don't see full 12 volts on these circuits, it's because there is a resistance between the 'hotwire' and the circuits. This resistance is most likely the resistor or resistance wire the connects to the coil + terminal.

So follow the wire from the + terminal of the coil to the keyswitch, and you should find the problem.

In my gallery, you will find a typical wiring diagram for a Duraspark ignition. This doesn't show the wire that goes to the regulator, but that should be in the same harness.

 

I think we have gone down a rabbit trail with the coil and the 5.6mv reading. 5.6mv is something we should not be worrying about right now, like the other poster said it could be noise.

When it all gets confusing, start over. You did the right thing, and went back to the alternator and re-verfied the problem, the field has voltage. I thought we had progressed to the point of finding the problem to be with the "s" wire on the regulator. I would try that again, to verify if the regulator is being told to turn on the alternator when it shouldn't.

I know it's a pain, but don't panic over this problem. If you need to use the truck, just put the battery cable on and then take it off everytime you stop to get out for awhile.

 

It is the 'S' terminal that I am thinking is getting power through the coil resistor. The reading on the 'S' terminal was 5.7 Volts, which is about 1/2 of 12 volts. We are looking at a voltage divider.

 

I just wen't out and checked, the 5.6 mV (not volts) reading is coming at the S terminal too (MM pos @ S Terminal, MM neg @ Batt neg). When the F wire is unhooked, that also drops to 0. This is still with the ignition switch removed.

Danlee - Thanks for explaining in a way that I can understand

 

Verify one more time, unless you did already and I missed it, that taking the "s" wire off fixes the problem on the "f" terminal.

 

Okay, I just went out and ran the DMM between the bat neg and the strap (showed the usual drain). When I disconnected the red/green wire, the amps jumped around (I think they went around 2) but I didn't pay a ton of attention to the numbers, because the battery started hissing like the fluid was boiling. Pulled the MM neg off, sound stopped, touched it again, started again... As long as the green/red is attached, no scary noises... Now what does that mean?!

EDIT: This happened with the ignition switch installed.

 

Do you have anything aftermarket added to this truck? Gauges, radios, winches, trailer brake boxes, etc.

Have you messed with anything lately, like changing the engine, tranny, restoration work, etc? If I remember right you said something about the engine being painted?

Trying to get some hints were to look. You have some wiring problems, and they were either caused by something somebody did, or a failure. If this is a failure, it's a very weird one.

Make sure and try to take care of your new battery during all of this. You definitely have a mysterious drain, and if you let the battery go completely dead too many times, it will ruin it. Make sure you have around 14v on the battery with the engine running. If you do, then at least the battery is being charged, and it should be ok to drive it, so long as you keep taking the cable off when you stop for a long period.

If it takes a fit and is not charging, then make your trips short, and when you get home, put the battery on a plug in charger to keep it up.

 

Let's also verify the connections. You have an ammeter in the dash, instead of a charging "idiot" light right?

So the battery + cable goes to the starter relay battery terminal.
Also connected to that same terminal is:

1. a wire (yellow/white) going to the A terminal of the regulator and
2. a wire (black/orange) going to the ammeter

The other side of the ammeter connects to:

1. the ignition switch and
2. the output (Bat) terminal of the alternator

Another pin on the ignition switch connects to:

1. the S terminal of the regulator and
2. the ignition coil, through a ballast resistor (or resistance wire)

The I terminal of the regulator is not connected to anything
The F terminal of the regulator is connected to the FLD terminal of the alternator

Does this all sound right and look right?

 

Drove to work today with no problems, but when I was on my way to the lumber yard, my truck suddenly started running really poorly, like it was misfiring. It was fine at higher RPM, but when I'm at a light, it's really rough. I pulled into a gas station and popped my hood, and my battery was making a lot of noise and had more fluid coming out of it. I unhooked the F wire, went to the yard, went back to the jobsite. Still running rough, but the battery isn't being overcharged.
I'm going to go mess with the idle problem right now. That's a problem I can find and fix (unless it's related to the elctrical system, then it's just another headache).

Franklin2 - Yes It's had a tape cassette player, an aftermarket Tach and trailer brakes added. None have ever caused problems (I don't even know if the trailer brakes work, they were on the truck when it was given to me). All have been disconnected since I've been having these problems.

I got the truck for free, and tossed in a 400 from a 76 Lincoln, which was rebuilt in Jan of this year, then the trans was rebuilt right afterwards.

I'd had no problems whatsoever until the starter cable melted to the manifold, after that all hell has broken loose (this forum has documented it well ).

grego - Yes, the factory ammeter in the cluster (looks like [D ALT\C] when charging).

Starter relay + side:
Large Black/Orange with fuseable link going to Batt terminal in Alternator. Spliced into this wire, is a large black/yellow wire going to the Ammeter, along with a small yellow black wire that leads into the cab (I think), also spliced in is a yellow wire to the A terminal of the regulator.

Regulator I terminal is empty, F terminal goes to field in alternator, S (red/green) goes into the center entrance of the cab (opposed to the driver's side, where many other wires go.
At the ignition switch, therre's no red/green wire, but a large orange (maybe faded red?)/green wire into "I2" pin in ig. switch, there's also a red/blue wire to the "ST" pin.

I have no idea about the ballast resistor wire, what pin on ig. switch would it plugged into? There are 9 pins. From top to bottom, ACC2, ACC1, ST, BAT, I1, (another labeled) BAT, I2, P2, P1

That's what I've got...

 

It looks like the shorted cable caused the problem. I am trying to think of other things this could have messed up, and one thing that comes to mind is the smaller ground wires going from the engine to the firewall and other parts of the sheetmetal.

The engine and tranny are mounted in rubber motor mounts, and the large ground cable bolts to the engine, so you need little wires coming from the battery neg and the engine block going to the sheetmetal of the truck. The regulator also needs a ground to operate properly.

Just something else to double check. The cable accident could have burnt some of these little ground wires in two.

 

You mean little ground wires, like the ones for the different electrical systems of the truck, or like the ground wires that that connect the bumper to the body, motor to the body, hood to the body, etc? The ones that look like woven metal (kind of a flat braided wire...)?

 

The flat braids are probably fine, takes a lot to take one of those out. Although loosening the bolts and retightening them again is always a good thing.

I would trace that red/green wire that goes from the S term on the regulator to the middle of the dash somewhere (I think you said). That is the wire that is turning on the regulator and feeding the field coil on the alternator. I would stick my eyes up under the dash and follow that one. It seems like it should go to the output of the ignition switch (whatever pin that should be). I could dig around and see if I have the docs for your main connector, but I don't have it off the top of my head. That wire should not be hot, when the key is off.

Man, I hope you work this out before that battery dies. I am amazed it is hanging in there. Ditto with the regulator.

My browser didn't quote understand what you meant by what the ammeter was showing when the battery was charging.

I wish we were doing better for you!

 

Hell, you folks are helping tons, no need to apologize. I'll follow that wire after work tomorrow.
I left all my tools locked up at the jobsite, just in case my truck craps out on me for one reason or another. It's not far up the road, so I'm just going to run it without the alternator, check it when I get to work, and charge it if I have to (I have my charger in my toolbox now). The battery cooking is what I'm most afraid of, as I'm sick of getting stranded...

I was just doing a half-@$$ed drawing of the ammeter in the dash , so don't worry about it.

Even if the problem isn't solved yet, everyone gets an A+ for effort...

 

You said a couple of things earlier that are interesting.
You said that after you hooked up your new alt and reg, that you smelled something burning under the dash. That kind of reinforces the theory that you might have a short in the green/red circuit up in there.

The other thing was the comment that while you tracing wires in the cab, you discovered the ammeter wire and hooked it up again. Was that before or after the point where you had everything working but then had a battery drain?

Make sure the green/red circuit isn't connected, or shorted, to the black/orange (like leading to the dash ammeter).