To start, I'm going to provide some back story. If that's not your thing I've provided a TL;DR summarization at the bottom.

I own a 94 F250 with the 7.5L 460. My headache all started a few months ago with a weird starter issue, basically it would start fine cold but would act like i had a dead battery when warm. As I was poking around I thought I would check the battery to block ground. I couldn't see where it grounded because of the damn smog pump so I climbed under to see if I could feel where it went. I found the cable with my hand and it snapped. All I saw was exposed and very corroded copper and all that was left were hard vulcanized chunks of rubber that was the wire shielding. At this point I was determined to do the following:

1. Replace the battery terminals and cables.
2. Replace the starter relay
3. Replace the starter
4. Replace the Alternator

I got brand new 2ga and 4ga wire, wire lugs, a lug crimper as well as parts (starter and 3g alternator from powermaster). At this point, I've bypassed large portions of the stock wire harness so I could tie in new positive and negative lines from the alternator and starter to the battery. I know I've wired everything correctly because all the electronics work. Dome light, head lights, power windows and locks. Everything is working. I can even start the truck but I'm not getting any voltage from the alt.

There's no external regulator on a 94 so I wired it according to powermasters instructions:

1. Cut off the stock ASI connector.
2. Wire green/red to green/red on the new alt connector making sure to put the provided 500ohm resister inline.
3. Make sure the yellow wire on the alt is connected to battery positive (it came out of the box looped back to the positive battery connection at the alternator.)
4. Wire the positive on the alt to the positive side of the battery
5. Wire the negative to a good ground.

That's it. Only that didn't work. I'm making as solid a connection as I can using solder and heatshrink tubing. I've since wired in the white black wire from the stock wiring to the stater wire on the powermaster plug. No change. I've verified the green is hot when in run. I've tested continuity from the + and - alt connections to battery. I've tested resistance from alternator to battery (less than .1 ohm on the - side and .2 ohms on the +.) I've checked voltage between the + and - connections on the alt, it shows battery voltage.

At this point the only wire I haven't connected is the yellow wire and this weekend I'm planning on tying that in to the + terminal on the alt.

TL;DR

My questions is this, has anyone done a 2g to 3g upgrade on their truck? Did it work great the first time or did you run into issues? Assuming you have everything wired up correctly, what are common reasons for these 3g alternators to not work. I'm basically just looking for anything I might not have tried. Any avenue of possible closure on this project of mine. Thank you.

 

call Powermaster tech support

 

no not a single person has ever and I mean ever replaced their 2g with a 3g. a forum search shows that no one has ever, believe me.
The positive if I dont recall correctly doesnt wire to the battery but to the starter solenoid (somoen tell me im wrong if im wrong)
Your "yellow" wire is wired to your alternator, is that the one thats separate from the plug(single wire) because if so THAT IS THE CORRECT PLACE FOR IT TO WIRE
Wire the negative? What negative? Your alternator case grounds ot your (engine brackets>engine>ground>battery ground path)

you played a lot with your wiring.. at no point I dont see where you wired your cluster telltale which excites your alternator to the alternator
Resistance battery to alternator is Nothing, that reading is meaningless. voltage drop while its running is soemthing but you dont have an alternator putting out juice yet.

Wait, you said you wired the yellow. now its unwired?!
Stator wire is connected to the truck harness?




You have motorcraft*, so the * is applicable

 

Below is a diagram showing how to wire a 3g. Green to green, yellow to alt output, and white (stator) to stator plug. I didn’t see in your post what you did with the stator wire. I also don’t know why you cut off the stock ASI plug as it’s the same between 2g and 3g.

 

I've done one. In the same thread user rla2005 also confirms he has done one.

Proof

 

I was being sarcastic lol

 

I swapped my 92 F250 4x4 460 2G with a 3G. Was walking by a 96 460 truck in a salvage and saw the alternator. Grabbed that and the harness, only thing I remember having to modify is the light green wire w/red stripe from original harness.

 

Why exactly is that? Doesn't the original 2G regulator connector snap right into the new 3G regulator?
But a new regulator connector came with the new alternator, so that worked out?

So far so good. And you verified 12v with the key in the ON position.

Your way is the "better" way, however thousands are out there with the wire simply connected to the BAT output and charge cable with no ill effects. It's supposedly less accurate there, but given a large, low resistance (6ga?) cable between there and the battery, there really is no voltage drop of note to skew the numbers.
Battery, or battery side of the starter relay, or the BAT terminal of the alternator, all work well for most.

That's the BAT terminal, correct? I assume yes, but wanted to be sure.

Where did you connect the ground? It supposedly grounds well through the case to the engine, but I've always added a ground as well. Just because...

I think this is your key right there. Got a pic of the connector at the alternator?
The White w/black stator wire goes only one place on a 3G. That's the small terminal in the side of the alternator near the regulator connector. Without that, it won't charge.
Even if it's supposedly connected there, verify because I've seen them slipped to the side of the actual contact point inside and not actually making a good connection. And it's hidden by the plastic end connector on the original plug, but yours might not have that anymore?

You have not connected the Yellow wire? I thought that's what you did in the beginning? It's still connected to the battery, correct? If not then that's another issue you need to resolve. It's there for sensing battery voltage and without it your regulator has no clue anything is going on. I don't know if it will simply fail to charge, or if it will overcharge because it does not sense anything on the wire, but it's not right to leave it disconnected.
However the missing White w/black stator wire is guaranteed (in most cases) to leave you without a working alternator.
I say "in most cases" because I once had a 3G work perfectly well without it. No idea how that worked out, but it did. Maybe it was a 4G in disguise?

Any chance we can see some pics of your setup?

Thanks

paul