Alternator wiring

[72hiboy4x4]

hey someone that knows what he is talking about......... me.......

[68F250]

Ok, I got my brain back.

But I see you guys already have the answer.

We are using the green/red stripe wire to excite the alternator. Like mentioned above, we need a diode inline so when the key is turned off, the alternator does not back-feed into the ignition and keep everything running. I guess I didn't think about that happening.

When it's running with the key on, I'm not sure how much current is exciting the alternator but I don't think it's much, maybe a couple amps at the most. When the key is off I doubt it's backfeeding that much current either. You could try the radio shack diode first and see, that's probably all you need. The end of the diode with the stripe should be the end that connects to the alternator. The other end connects to the green/red stripe wire. That way current can flow from the wire into the alternator but it can't flow from the alternator back out the wire.

Thanks again guys!!

[Docholiday72tx]

Fellows, I understand the whole concept of the diode and the alternator back feeding the ignition. The problem is the green wire with the red stripe still isn't making my amp guage work. Also, that wire isn't necessary to excite the alternator.
The alternator actualy has 4 wires coming off of it. There is a ground wire which I have fastened to the bolt on the side of the block where the battery ground is. There is a plastic plug that goes in to the alternator that has a red wire and a brown wire. The brown wire is currently loose and not hooked up to any thing, and this is the same wire I tried to use to make my amp guage work.
The other wire on that plug is a red wire which I have soldered to the 4th wire coming off of the alternator which is also a red wire. I have both wires run up to the starter solenoid and attached to the big stud on the battery side that the + side battery cable is also attached to.
With the alternator wired this way, I get 13.98 volts with all accessories and lights running at idle. How ever, there is still no amp guage.
Any one have any bright ideas?
Doc
Also, wouldn't it be a good idea to put a fusible link in my big red wire between the solenoid and alternator....just to be on the safe side?

[68F250]

The red/green stripe wire has nothing to do with the amp gauge, it is not part of the amp gauge circuit. The only thing that wire did was energize the regulator to feed the field current. The amp gauge circuit is attached in the original harness that had the heavy wire that ran from the alternator output to the starter solenoid. You have to use that original harness connected from the alternator output to the starter solenoid in order to utilize the amp gauge circuit.

[68F250]

The gauge should work fine, it doesn't know what kind of alternator is connected. Use the existing harness but only connect the heavy alternator output wire, fold back and tape up the other wires.

I knew I mentioned it before. Sorry I don't think I explained it well enough why it needs to be used.

Here's the deal, trucks with an ammeter are the only ones with this red/green stripe wire (cars too). This wire connects to the 'S' terminal on the regulator to energize the charging system. The 'S' terminal on the alternator is not used. That's all the wire does. It gets it's power from the ignition switch, the same point that the resistor wire does.

There is an additional shunt circuit in the harness from the alternator to the starter solenoid that runs the ammeter. You need the ammeter connected to that shunt circuit and also the heavy wire connected to the alternator output and the starter solenoid. That's why you have to use the existing harness.

Trucks without an ammeter use the 'S' terminal on the alternator to feed the idiot light which then feeds the 'S' terminal on the regulator to energize the charging system.

I hate to say this but even when these trucks were brand new, the ammeter hardly deflected at all. It's just the way they were. Hate to see you go thru so much trouble only to get a tiny deflection. Ya know what, since you've run all new wires anyway, it would be ideal just to redesign a new shunt and make your meter work like it should have.

The car line with ammeters had the same inherent low deflection, there were some service bulletins about it. The answer was to explain to customers that that's the way it is. Funny thing though, I guess enough Tbird owners complained because they eventually got one that was redesigned to deflect a lot, a whole lot. It would peg after startup. Then there's another service bulletin after that to explain to Tbird owners that the wide deflection was normal. Kinda amusing.

[Docholiday72tx]

I have run all new wires and I was thinking it would be best to make my own shunt also and make my meter work like it should. The trouble is....I'm not sure how.
How do I go about making this shunt to make my meter work?
Doc

[68F250]

I don't think we've ever figured out what the shunt value is. Attached is the wiring diagram and shows the shunt as a dotted line in parallel with the ammeter. It's gotta be a pretty low resistance value or else it would drop too much voltage and cause other problems. Maybe that's why the ammeter doesn't deflect that much. It's just a short length of smaller gauge wire placed inline. The ammeter is in parallel across the smaller gauge wire and reads the voltage drop and polarity. I'm guessing it's in the millivolt range. It works the same way the ammeters you use for troubleshooting. They supply a metal bar for the shunt that's placed temporally inline with the battery.

Here's something interesting I found doing a search for Ford ammeter shunts on the web:
http://automotivemileposts.com/garage/v2n7.html

What about just running a voltmeter instead?

[Docholiday72tx]

I didn't want to hook up a volt meter or a light because I wanted everything on the dash to work correctly. How ever, it is increasingly obvious that I'm not quite smart enough to hook up the factory amp guage, so a volt meter or light may be my only way to know what's going on with my charging system.
Does any one know exactly how the factory amp guage hooks up?
Doc

[willowbilly3]

FWIW the autolite is a better and more trouble free alternator than any Delcotron will ever be. I would not change just to simpligy wiring. The regulator is the main problem with the stock setup and if you will by one from Ford. (autolite or motorcraft) it won't give you problems. ALL aftermarket voltage regulators are junk. I'd rather get an autolite from the junkyard.

And FWIW, those stock amp guages seldom work and even at best the needle migh move a couple needle widths when the alternator is full fielded. I would just install a volt meter someplace and plant a little cactus where the amp guage goes. Watching it grow will be more activity than the guage showed.