2G ALT, New VR connector with 3 wires

I hope it's ok to ask for help here. I'm trying to help a new member over there figure out which wire to use on the new 3 wire VR connector when it's installed on a new 2G ALT. Gary, would you know the answer ? The schematic shows the wrong placement of the green/red wire from VR on 2G ALT, Connector C186. My C186 has the yellow/white and green/red next to each other, yet the schematic shows them separated...


https://www.ford-trucks.com/forums/1740652-fml-new-alt-isnt-charging-please-help-4.html

Yes, it is fine to ask for help here for someone on FTE.  There's lots of good people there, and particularly Dave/Franklin2.  So if you have him helping you then I probably can't be of any more help.

I say that because all I know about the 2G is what is in the EVTM - the '86 EVTM as the '85 EVTM shows a 1G.  But I find it really strange that there are two different voltage regulators for them that have different connections.

Anyway, sorry but I've read through the thread and don't have anything to add.  I'd follow Dave's lead.

Why did the guy change the regulator plug?
If you read the TSB it says to replace the charge connector.....

Yes, most new 2G's come with a hard wired pigtail and heat shrink butt connectors (to get rid of the faulty plug blade connectors)

The two hot (bk/or) battery leads from the 2G should go to splice 202 which feeds the cab through Y-37, the far side of the shunt B/O-38 and the far side of the ammeter  Y/LG 654.
At the other end of the shunt (S203) we have the Y/W "sense" wire going to the regulator and the R/O wire(also coming from C610) that feeds the ammeter.
These all join a  single fusible link at Splice 203 before attaching to the always hot stud of the starter relay.

The choke should be feeding from the white & black at the 2G output (not "from ignition on") because if the engine stalls while warming up the choke will continue to open.

If his regulator is labeled( A S I ) then he doesn't need to feed stator current to the center wire, but he DOES have to connect the Y/W "sense" wire to A and the LG/R (trigger) ignition on wire to I.

Edit: I see in post 37 his regulator is indeed labeled ASI. So, he only needs the two end wires connected.

The '86 EVTM has the correct diagram..

Thanks for replying.

In post 48 over there, you'll see where my 86' 302EFI has the VR wires next to each other. That's the 2nd replacement 2G in the past 5 or 6 years. The ALT was installed Nov 2021.


The OP in that thread said his connector at the VR was melted, there's a picture it earlier, but I'll say it didn't look that bad.

Is your regulator labeled AIS?

Honestly, I don't know why anyone would go back with another 2G.
Marginal charging and cooling. I had a couple of rectifier boards go bad.

But it took me only one time cooking that charge plug to realize it wasn't one of Ford's "Better Ideas"

I see RYans460 just signed up over here.

Hopefully we can give him the answers he needs....💡

All 1986 G2 alternator voltage regulator plug I have seen are not wire per the diagram above.

A long time ago, Gary had a 2G to 3G conversion page with a photo of the alternator harness. It matched everyone I have seen. With the green wire going to the center "S" input. Just 2 wires.

There was an old thread... When Gary was asking for input, as he was making a 2G to 3G info page. The 2 wire plug VR was talked about then, in that thread.

Jim number 2

https://forum.garysgaragemahal.com/Help-On-3G-Page-tp86569p88610.html

Appreciate the link.

This forum is indeed an enigma sometimes...

Jim, from what I can tell from that other thread is that the 3wire plug is physically adaptable to the 3G swap, but not necessarily without changes. The real issue is how many different variables came from the factory.
The above diagram shows the VR "S" not used and the green wire connected to VR "I". This is the only diagram that shows this, but it's the easiest next step as this is how I have it currently(not working for those not following the FTE thread) wired.
I will cut the Stator to VR "S" wire and see if anything changes.
If that doesn't work, I will move the Green/red wire from the VR "I" to the VR "S" like my truck was before this debacle.

Max, in one of your pics it looks like your ALT B+ wires are divorced.
The diagrams/schematics and my original wiring all show those two splicing together.
Do yours splice out of picture frame, or how do they route to the solenoid and wiring harness?

Hello everyone. Thanks for having me here in the Garagemahal.
Long time reader....first time caller!

One of the issues with the 2G alternator is the wiring Ford's "engineers" used (maybe they were borrowed from Ford's British acquisitions?). All the power for the 1986 trucks (probably 1985 also) went through the alternator harness. There was a wire used from the alternator that the shunt ammeter was in parallel with, this, in theory, measured the current going into or out of the battery.


If Fuse Link J fails while driving, the truck will continue to run as long as the alternator is capable of handling the demand, but, Circuit 36, Yellow/White is the voltage sense for the internal regulator, so it is essentially reading the battery voltage. If there is a heavy drain on the system, more than the 65 amp 2G can maintain voltage at the set point, it will start raising the voltage, here come the mysterious light failures.

I am sure that the theory behind this was to prevent overcharging the battery since the shunt + ammeter leg has enough resistance so the ammeter gets a usable signal. Chrysler used an actual full in-line ammeter, which was more of an alternator output meter. The ammeter on our trucks if I remember correctly (Darth now has a voltmeter) indicates + when power is flowing to the battery and - when it is flowing out of the battery. Those of us who are old enough to have driven vehicles with generators and an ammeter are very familiar with the wild swings.

Lebaron, I will tear off the corrugated loom tomorrow and double check my wiring.
In your diagram(which I have viewed many times....) the VR "A" goes to the Battery(Solenoid).
I don't trust myself and it's possible I have "A" wired to the harness and both ALT B+ ran to the solenoid....but if that were true would the solenoid and truck start/run normally? Wouldn't that solenoid "act up" if I had double the signal from the ALT? Would the key even correctly activate the solenoid and starter? I think I'm safe but I'm capable of peeling some tape back.

I understand the ammeter is really an "overcharging or undercharging" meter and not a voltage tester. Mine stays stationary in the center whether the battery is disconnected, the lights on or the engine running, it doesn't jump when I start the engine....  My neglected/miswired ammeter doesn't work.

Max, check out this Pic of the melted ALT plug that need replaced. The VR plug just broke off the mounting tab. I could reuse it, but dodgy.
IMG_20231104_103301432_HDR.jpg

I changed the VR plug because the mounting tab broke off.

S202 is just before the Solenoid B+.
Both voltage and continuity test confirmed many times.
My B+ after S202 had to be spliced and is the blue heat shrink in the pic below. Yellow and Black leaving S202 should be ALT B+ and VR "A".
What is the little red wire?
The Small yellow wire(Not VR"A") I think is the ammeter wire. It goes to the harness splice and into the firewall Should that be spliced to ALT B+ or the VR "A"?
The dirty green wire I'm holding is the VR green wire. It's currently on "I" but I will be moving it back to "S" tomorrow.

Did I get that right? Does my pic look right?

That is the classic 2G failure, and it wasn't just trucks, Taurus, Tempo, Crown Vics virtually any Ford with a 2G alternator was prone to spontaneously ignite. (Ford was just giving us a preview of what owning an EV could be like) I haven't had a 2G alternator on anything since about 10 years ago when I converted my truck to EFI and put a 160 amp 3G on.

Middle terminal on the regulator plug is not used on a 2G, it is used on a 3G. The Yellow (37), BK/O (38) will be either 10 or 12 ga as they handle the alternator output and power feed to inside the cab (basically everything).

If you want to ensure that you don't get a runaway alternator, move the Y/W (36) wire to where the BK/O splices to the Y. This is how the 3G sense circuit is, picks up the output at the alternator.

Splice 202 should be out in the harness.
Look how it picks up both the shunt and the 'downwind leg' of the ammeter (Y/LG 654) as well as the main feed to the cab (Y 37) before Connector 610. Then the thicker yellow 37 splits into two fusible links (S101) in front of the blower plenum.

The shunt wire (B/O 38) across the ammeter is a very specific resistance under load.
I think more likely you've spliced a fuselink under the blue heat shrink, and you're showing S203

If this is the case, R/O is going to be 655 going to the battery side of your ammeter through C610.
The yellow zip tie is definitely attached just next to the engine bay side of C610.
And the LG/R wire in your hand should go to (I) of the voltage regulator. (Jim's Rebel says it goes to (S) on a 2G, and frankly I don't recall that long ago)
I do agree with Bill (85Lebaront2) that the 36 Y/W sense wire is better off attached at S204 where the two output wires join.

The Green/red in my hand is currently on "I". It doesn't work(or the ALT is bad).
It was previously on "S" and a I plan to try that again, as that is how my truck previously worked and I was already convinced it should be the way your saying.

I think you're right about S203/S202
I will doublecheck my wiring shortly. Just waking up.
Where is the multi-wire splice/connector(right edge of my Pic) in the diagram?
 

Certainly try it connected to 'S' if that's how your truck was working before.
I know you've said that you tested all wires for voltage before, but I've got to ask you, if you turn the key to Run (without starting the truck) does the battery warning lamp in the cluster stay illuminated?
Does that LG/R wire have nominal 12V???

Look at the diagram.
C610 is shown in four different places, but it's there.
This is one of the idiosyncracies* of the way EVTM's are laid out.
I'm on my phone so it's a bit of a challenge for me to highlight it in all those locations, but rest assured that it is all one connector (on the  right side of that pic)



Edit for clarity: this photo from Gary has the 2G harness with the splices and plugs called out.

Ahhhh thanks for spotting C610. That makes sense. I was looking for one "splice" like it is physically in the truck.
My "battery warning" lamp has never illuminated.... Probably doesn't work like everything else... FML. Neither does the "Brake" warning light.

PO of my truck was very neglectful. Mice chewed wires and eventually caused a fire under the hood. His "backyard mechanic" managed to get the truck running again after the fire, but he left vacuum lines, wires and sensors completely melted and connected. The EGR and dual Smog pumps still fully connected, but none of the vacuums and sensors working.
My first step of ownership were to replace the Motorcrap Carb, remove all the BS and fix leaks. The truck has ran great for 10k miles.