Vintage Mustang Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
261 Posts
Discussion Starter #1
So I have a 3G alternator for my 67 Mustang. Now I had it wired up to my old wiring harness and had it working just fine. But now I am installing the American Autowire harness and I'm not 100% on some of the wiring. According to the wiring diagram I see there is a three wire connector that plugs into the back of the alternator with a black/white wire, yellow wire and red/green wire. So the black/white plugs into the other terminal on the alternator and the yellow wire needs a constant 12V source. But, I'm not sure what to do with the red/green wire. I don't have the ALT/GEN warning lamp so do I just hook it into a 12V switched power source? Or do I need to add a 560 Ohm resistor in there as well?



I believe originally I had it hooked into wire 904 in this figure



Thanks.
 

·
Registered
Joined
·
261 Posts
Discussion Starter #3
Ok American Autowire is now confusing the hell out of me. I called their tech line about this and their instructions say to connect the brown wire from their kit to the yellow wire on the 3G harness. Well their description of this brown wire is that it is the trigger/exciter wire that is switched 12V. Well it would make sense to connect this to the red/green wire right? They say to leave the red/green wire unconnected because I don't have the ALT/GEN warning lamp...
 

·
Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
Joined
·
20,639 Posts
If you leave the green/red wire disconnected, the alternator won't work. That wire "tells" the alternator that the ignition switch is on. The circuit was meant to have an alternator light in it, the resistor is simply to simulate a light bulb if you choose not to use one. I like red lights shining at me to alert me to problems. Thus I have a voltage gauge and I added a warning light. I have an oil pressure gauge and I added a warning light for that too.
I've never been clear why you need a resistor and/or light in the green/red wire circuit. I do know that Ford used them. In Crown Victoria wiring diagrams (for example) the resistor and warning light are clearly shown in parallel. I expect if someone cared to search enough, somebody out there knows what the purpose of resistance in that circuit. Evidently the 3G will function without that resistance, but is it working optimally? It may be for something we don't even care about like later 6G's where the engine computer turns off the alternator while the engine is being started. I don't know.
 

·
Registered
Joined
·
759 Posts
The resistor is there to force the exciter wire to pass through the bulb, thus illuminating it at start up or if there's an issue with the alternator's charging (path of least resistance). If the bulb burns out or is not in the socket the exciter wire will go through the resistor and still allow the alternator to charge.

As for the wiring aspect, the internal regulator's I terminal is the indicator/exciter trigger and needs to be connected to a 12v switched circuit. When you say brown wire, I presume you mean from the AAW harness? If that is a switched 12v wire or is labeled "alternator exciter" or "alternator turn on" etc. then the brown wire should be connected to the red/green wire at the I terminal of the internal regulator. The yellow wire is simply connected to the B+ stud of the alternator (it doesn't need to run to the solenoid like their drawing)...

See this for help:
 

·
Registered
Joined
·
8,661 Posts
Heh, thanks StrokerDude. The resistor makes complete sense now. The ohm rating is higher than the resistance of the bulb, so electricity will take the path of least resistance through the bulb! Can't believe I couldn't figure that one out.

airmenair, does the AAW harness try to use the same wire colors as the factory? IIRC the brown wire is on the "S" post of the starter solenoid and the red/blue is on the "I" post. I would think their brown wire would only be hot when the key is in the start position and off when in the ON position.
 

·
Registered
Joined
·
261 Posts
Discussion Starter #7
Thanks everyone for the responses. I know what to do now. I'm going to have to double check with American Autowire regarding their instructions because I believe they may have a mistake.

buening, no the AAW harness doesn't use the same colors.

AAWs description of this brown wire:

"This wire is the exciter wire for your alternator/voltage regulator. If you are using a one wire alternator, this wire will not be used and should be capped off as it is "hot" in the ignition "on" position. If you are using an alternator that requires an internal or external voltage regulator, this exciter wire must be connected to the "switched or 12V ignition" terminal on your regulator or alternator according to the manufacturer's specifications for the type of alternator/regulator that is being used. (AAW recommends a GEN 3 Internally Regulated or 1 wire unit)"

Now this is the adapter for the 3G alternator to their harness. Now unless the deliberately switched the yellow and red/green wires then I'd say something is fishy here.


The wire on top is red/green.

Am I the only confused at the logic here?

Thanks again.

Also: Big help from Gypsy and Stroker, thanks!
 

·
Registered
Joined
·
8,661 Posts
The yellow is the constant hot 12v wire and the red/green is the switch 12v (exciter) IIRC. My yellow wire has a ring terminal on the end and is attached to the charge post of the alternator. It supplies power to the regulator, and that charge wire is hot all the time. At the top of that diagram, it states that "A" terminal to "B+" post

Below is the harness I used from Ebay.





A one-wire alternator is self-exciting, which is why they say cap it off in that instance. I say connect the brown wire to the red/green wire on the regulator since they claim it is their "exciter" wire. Is this how you were interpreting this?
 

·
Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
Joined
·
20,639 Posts
Doh! I see now, chalk one up for StrokerDude.
No wonder it works with just a direct connection, just a resistor, or just a lamp. It doesn't NEED the resistor it's just a better choice to have a light with a backup.
A direct connection with just a wire is OK, as long as you have voltage gauge or ammeter to keep an eye on things.
Just a lamp is OK, as long as that lamp never burns out while you are driving and you don't have a gauge.
And running just a wire with a resistor would be pointless.
 

·
Registered
Joined
·
759 Posts
Thanks Gypsy for the kudos. Wiring is kind of my thing and I've done a lot of these 3G upgrades/conversions...

Airmen, look at the drawing I posted above and match the terminals to your connector (as it would plug in) and wire accordingly, color be damned :).

I understand what they're trying to do, but it's less wiring to wire it like Buening and I have stated.
 

·
Registered
Joined
·
261 Posts
Discussion Starter #11
Thanks Gypsy for the kudos. Wiring is kind of my thing and I've done a lot of these 3G upgrades/conversions...

Airmen, look at the drawing I posted above and match the terminals to your connector (as it would plug in) and wire accordingly, color be damned :).

I understand what they're trying to do, but it's less wiring to wire it like Buening and I have stated.
Thanks I'll plan on doing that. That diagram you posted was a big help, thanks for that too.

Another question. I have the factory ammeter/voltermeter (whichever it is). Most things I've read suggest not using this thing. What are some good aftermarket voltmeter/ammeters and do they sell ones that work in the standard 5 gauge cluster? My gauges are stock except for a mini tach that I've installed in place of the clock.

Out of curiousity, you say you know what they are trying to do. What would that be? Because I'm not very sure myself, I thought they just made a goof.
 

·
Registered
Joined
·
759 Posts
They are having you do extra wiring. Just like the yellow wire shows going to the solenoid when it can go right to the B+ on the alternator. They are having you run two wires, one for the exciter and one for the lamp, when you can use one wire to do both (as shown in the drawing I posted).

Honestly, the stock Ammeters are not going to handle modern high-output alternators like a 3G. If you have a stock 35-66 amp 1G that's one thing, but a 95-130 amp 3G will smoke the gauge/wiring. It's best to simply not hook it up. You can probably have it converted to a voltmeter by a company like Autoinstruments.com or another gauge restoration company, or you could build your own cluster with an aftermarket housing and gauges. All depends upon your budget, skills, time, and the look you want.
 

·
Registered
Joined
·
1 Posts
Thanks to all who posted reference gen 3 alternator and American Autowire harness. I had contacted them 3 times and got wrong info each time. With the info on here I now have an alternator happily alternatoring away. Thanks again to you all.
 

·
Registered
Joined
·
905 Posts
The resistor is there to force the exciter wire to pass through the bulb, thus illuminating it at start up or if there's an issue with the alternator's charging (path of least resistance). If the bulb burns out or is not in the socket the exciter wire will go through the resistor and still allow the alternator to charge.

As for the wiring aspect, the internal regulator's I terminal is the indicator/exciter trigger and needs to be connected to a 12v switched circuit. When you say brown wire, I presume you mean from the AAW harness? If that is a switched 12v wire or is labeled "alternator exciter" or "alternator turn on" etc. then the brown wire should be connected to the red/green wire at the I terminal of the internal regulator. The yellow wire is simply connected to the B+ stud of the alternator (it doesn't need to run to the solenoid like their drawing)...

See this for help:
I know this is an old thread, but I would really like to see this diagram if anyone has it.
 

·
Registered
Joined
·
905 Posts
I was looking for the one in post 5. I know it's a long shot, I'm just looking for a few more details for wiring a 3G alternator with the AAW wiring harness. I am sure I am over thinking it, but going from scratch, I have no reference to go by. If I go with a 3G, it appears I do not need a regulator, and I have a Pentronix Flamethrower d1352 distributor, and it says I do not need a coil with it. So do these two items eliminate the use of these items, and I just wire directly to them and there is no outside things to add?
 
1 - 16 of 16 Posts
Top