I have been lurking here for a while and have finally registered. This is my first post. Thanks for all the help in the past, and I soon hope to make my contributions.

I think I have my wiring figured out but I have a few questions that have not been resolved after copious searching.

First, my truck has the 300 I6 in it and I've done the 2G to 3G (130 amp) conversion. I am reusing my old wiring harness. The 2G harness has two wires from the voltage regulator: A (yellow) and S (green/red). In it's original configuration, the "I" terminal on the alternator has no wire, and the stator wire runs to the electric choke.

I have used the old voltage regulator D-plug as the A-S-I wires are in the same positions. For the output, I have spliced the wires together and simply attached them to the battery stud on the 3G alternator with a common ring terminal and added a 4g wire running directly to the starter relay (this will be fused with a mega fuse). Everything "seems" to be working fine. At the battery terminals I have 13 volts with the motor off and a bit over 14 with it running.

As much for my own understanding of how the charging system functions as to make sure I have done this correctly, my questions are:

1. Do the 2G and 3G use the same internal voltage regulator?

2. Does my original 86' 2G harness not have an "I" wire because I have an ammeter in the dash?

3. With the 3G, do I need to splice the stator wire into the "S" wire ?

4. Does the original red/green wire (the S wire on my harness) on the D-plug provide the on/off juice from the ignition to turn on the alternator ------ and is that why on diagrams out there for the 3G, the stator wire connects to the "S" wire on the regulator?

Thanks for responding and if you have any other suggestions for the swap, they would be appreciated.

 

"I" is the lightgreen/red wire. I have never seen a configuration on the newer alternators where the "I" terminal is not used, but of course I haven't seen everything out there either.

It may be also that all the 87-up trucks used the idiot light and a voltmeter, so that's why they use the "I". Possibly the 86's with the ammeter where different, though my other diagram for a 86 is not that clear about it. The 86 diagram does seem to use less wires though they are not labeled.

 

1) No
2) Yes
3) No
4) Yes

Hope this helps.

 

The voltage regulators, 2G to 3G have different P/N… most likely due to the higher field current requirement to provide 130 amps output.

I have been researching this same 2G to 3G swap, we have the same year truck with the same engine.

https://www.ford-trucks.com/forums/9...ml#post9296994


The only thing I am not sure you did was move the small wire in the power output plug to the single stator plug on the 3G. Is your choke currently getting any voltage? It should be getting around 6-7 VDC when the engine is running. Is anything connected to the single stator connection on the 3G?

Here is a photo of a stock 2G for our trucks, it is my ride along spare.

The wire that powers the electric choke is the one with the pink/red butt splice in the picture.

What ALT case style did you use? What was the 3G removed from, make - model??
Jim
.

 

Here's a side by side shot.
You can see the regulators on the back.

 

Thanks for the responses.

Jim, that is exactly the alternator configuration I had. It seems like our trucks have an anomoly wiring set-up... eg. the green wire running form the "S" terminal, and no "I" wire. I never had the stator wire from the 2G output plug connected to the carb and now it is not connected to anything either. The truck has a new motor in it with a few mods and changes from the stock configuration, and it runs great. Have you done your conversion yet? How did you or are you going to wire it?

On the other hand, although the 3G is charging, the way I have it wired, I've lost a few ignition switch powered circuits (such as my stereo). I've missed something. Could this be the stator wire or should I just go get a 3G, three wire pigtail and go through it again?

I honestly do not know what the alternator is out of but it is a direct bolt in save the V pully. I bought it from a local alternator builder.

 

Does your 3G ALT look like the 3G one in post #5. They come in “long ear” case style which is 8.25 inches wide bolt spacing and “Short Ear” case style like the ones shown in post #5, short ear ALT have a 7 inch bolt spacing. Your original 2G was 7 inch bolt spacing. More photos in the link I posted in post 4 of my mounting bracket and the different 3g case style. There is a forum just for the Ford Inline Six with a good 3G ALT thread there also.

I plan on wiring my 3G the same way you did, but I need to use the 3G stator plug (output) to heat up my electric choke.

Are you still using the original ALT engine combo mount, that also mount the air pump about the ALT.
True is… I haven’t really figured out which case style will fit in my mounting bracket. But I might be able to do a trail fit at the junk yard if I can find a truck like mine there.


More thoughts…
Do you have AC? Do you have a single V drive belt. Most say a single V belt is only good for around 90 amp output before it will slip. I have AC and a single drive belt so I am looking for a lower amp 3G ALT.
The extra 4 g wire will most like make you amp meter read incorrectly.

 

My 3G has the 8.25 bolt spacing. It fits into the original location with no modification under the smog pump, which I no longer have on the truck. The swing arm slides down a bit to accommodate the larger case. I understand that the only problem with many of these is that they are not tapped, so you'd only need a bolt with a nut on it to tighten it down. There is plenty of room down there even with the radiator hose underneath it. I do not have a/c and am using a double V-belt system just like before. The amp meter isn't really important to me as I've got a volt meter wired in the cab.

As for the 3G wiring, I did not have time today to recheck it. (Incidentally I am also in the process of putting in a dual battery set-up). I will do that tomorrow. I may look into the newer three wire connector. The problem is that the original output harness has a cluster of wires spliced into it that end up in space if I follow the standard 3G wiring diagrams. I'll let you know how it goes.

This discussion has pictures of a harness like my original:
FullSizeBronco.com - 78 - 96 Ford Bronco offroad club, forums, tech, installs

...and a somewhat inconclusive talk about the correct wiring scheme.

-Kris

 

As it turns out, my wiring solution is correct for my truck. After several conversations with different people, including a great mechanic and a gentleman who has been building alternators since the beginning of time, I learned that the 2G voltage regulator plug I have is fine for my truck with the 3G alternator.

Here's why: My truck does not have an idiot light but a ammeter. Although both the 2G and 3G have A-S-I terminals, without an idiot light the truck only needs the A and S terminal because the voltage regulator can be excited through the S or I terminal. So the "I" terminal has no wire going to it. The ignition-powered wire (green and red) just goes to the "S" terminal. The stator wire then (the white and black wire on the 2G that shares the same pigtail as the double output wires, or the black and white wire on the 3G that has it's own independent plug-in), goes to the electronic choke on the carb carrying around 7 volts. In this truck, the 3G can safely be wired exactly the same way.

Incidentally, the ignition circuits I lost were unrelated to my wiring scheme. I somehow, simply blew a couple fuses while having things apart. Everything is working fine now and charging at a constant 14.2 volts regardless of the draw on the system. I drove my truck around all afternoon...all things go.

If anyone is interested I can post pictures at some point of the wiring scheme and the alternator set-up I have on my pick-up.

 

The single pulley is good for 100A or a little more before it slips. (at least in my experience.)

You can get a 2 belt pulley @ RJM Injection.
RJM Injection Tech Alternator Accessories & Parts

 

Thank you for the follow up post Solo.

If you get the time a picture would be great.


It is good to know it will work as is... without having to reworking the voltage regulator plug. Most all 3G write ups I have read use all 3 inputs on the voltage regulator.

Also I do have a 2 V pulley, but the outer V grove is used to run the air (smog) pump above the ALT

Jim