Ammeter wiring?

[motzingg]

Found this excellent article on a mustang forum
http://www.allfordmustangs.com/forums/c ... iring.html

I think this explains the wierdness of the alternator wiring harness in my '68 bump. I swapped in a 2g alternator but i'd like to get my oem Ammeter working to let me know whats going on, especially in the summer with an electric fan now.

Does anyone know if this is the same way its hooked up in the bump? I'm usually pretty good at puzzling out wiring schematics but the way the ford ones are drawn confuse the hell out of me.

Otherwise anyone else have a working ammeter on a late model alternator? How'd you hook it up?

It should be as simple as some kind of ballast resistor (the wire serves as a resistor) and the two wires going to the ammeter being the voltage probes... but i'm not sure.

[Nitekruizer]

From what I can tell, the AMP Gauge circuit for our Bumps seems to be wired the same as that diagram. Looking at it, you have to wonder why it even works!

The yellow wire from the gauge connects to the main wire that runs between the Alternator's "BAT" terminal and the main terminal of the Starter Relay. The red wire from the gauge connects to the main terminal of the Starter Relay. Both wires are protected by inline 4 Amp fuses. I guess in the odd event that something were to happen to the black wire, the fuses are there to prevent full current from flowing through the gauge.

Anyway, I would think that the wiring of the Ammeter would be the same, regardless of whether the alternator uses a built in regulator or an external regulator. The gauge appears to essentially be connected between the Positive (+) terminal of the Battery and the Alternator's "BAT" terminal, in parallel with the main black charging wire. I'm not sure if the first section of the main black wire at the Starter Relay is a Fusible Link or just regular wire.

That's my basic interpretation of it all anyway.

[motzingg]

thanks, yeah that is along the lines of what i was thinking.

i'm trying to puzzle out if the voltage being measured is across the main battery line or if it is measuring the power from the VR that is going to excite the alternator?

the molded junction block in the stock harness might have some other voodoo wierdness in it... who knows. I'm in the process of figuring out how to re-wire the truck now, so i'll just throw away the stock ford and come up with my own system.

[tqwrench]

The ammeter in our trucks measures a very small voltage differential across a known resistance wire and interprets that as -/+ charging. It's crude and prone to problems. I think the meter in my truck is shot, there are reproductions that look nearly identical that fit perfectly in our dash that will read voltage directly to us. I think I'm going that way with mine.