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I've got a 1970 F-250 with the 360 FE engine and I wanted to do the 3G alternator upgrade because it looked pretty straight forward and Painless Performance had a nice wiring harness to do the job.
Unfortunately, just being "easy" doesn't mean I'm able to sort this out it seems.
I'm pretty confident on the charge wiring setup, but it's all the extra wires that I'm left with in the loom and which specifically will achieve my goals of 1) giving power to the cab, and 2) allowing the whole shebang to start up. I've removed the original voltage regulation devices because I had read these were no longer necessary with this setup.
3G Wiring Mess
Here's the scene and pardon the mess. I've placed numbers on the areas of concern presently. Which isn't to say I haven't borked something else up completely.
3-pin OEM plug. Heavy Black wire with yellow stripe, red wire, and yellow wire.
2-pin OEM plug. Yellow wire with green stripe, Green wire with red stripe.
Yellow wire from Alternator (this is supposed to go to the positive side of the solenoid and that's where I've hooked it up)
Green wire with red stripe (this should go to a switched wire)
First Question: Should the green/red wire from the Alternator connect to the green/red wire on the 2-pin plug?
Second Question: I'm pretty sure those remaining wires need to be reconnected but at this point, I'm not sure where. Should they all just connect to the positive rail?
Here is a good swap thread. This one says yes on connecting green/red wire on alt to green/red from the truck wiring. I have the stuff to do this swap but havent got to it yet on my 72 f250. Good luck. https://www.ford-trucks.com/forums/8...-pictures.html
Okay, that makes a bunch of sense. I'm going to try that here shortly.
Now the question is, there's four remaining wires in the Loom, what is to be done with them? I was reading that one of these wires sends power to the cab, but of course in that thread they were dealing with a different model year truck.
@1browski 's tip was the kick I needed. I mean it's so obvious I completely overlooked it.
So I made green/red to green/red connection, and then all three connections on the 3-pin plug were sent to the positive rail of the starter solenoid. I drew this conclusion based on the wiring diagram that basically showed all these were tied together in a complex, yet interconnected web of wiring. That leaves the other wire from the 2-pin plug (Yellow/Green) disconnected. From the wiring diagram this wire took voltage from the now removed regulators, to some sort of switch that's purpose isn't labeled in the diagram. I left enough wire if it becomes essential that I reconnect it somehow.
Anyway, I finalized the wiring and tried to tidy it up a bit, and here's the finished mess. Those distribution boxes sure do help a lot.
Looks nice and tidy. How did your alternator clearance on that head? Did you have to shim it out or anything to get your pulleys lined up. I cant wait to get that far along on my truck.
Well, y'see the screw for the grounding terminal is actually in contact with the head and I used a low-profile, button head screw too. I don't think this is ideal, but since it's all bolted securely I think it will be okay. Ideally I think I would extend the upper bracket to allow the alternator to rotate further count-clockwise so the screw could clear the head.
As for the pulley, it was necessary to insert a shim as the pulley itself wouldn't clear the alternator housing. So I bought some brass shims from McMaster-Carr (they were the only place I could find them). https://www.mcmaster.com/catalog/127/3514
The alternator I bought (NAPA part # NNE 1N3087) was completely designed on a metric standard though so the 5/8" ID was a little too small, but I reamed it out with a step drill and it was fine. The .045" thickness is the real key as it allows enough threads for the nut to engage. Otherwise, the belt alignment looks to be fairly spot on.
When I did the 3G upgrade I abandoned the ground screw and moved the ground wire to one of the 3 bolts that hold the housing on. The alternator barely kisses the head...could slide a piece of paper between the 2. I didn't use a shim on the double v pulley on mine and it lined up.
Great thread. I did the 3G years ago on my bronco. I could not get the V belt to stop squealing. Eventually I upgraded the whole front dress to the explorer serpentine and 4G alternator.
One thing that I did not see mentioned, is if you have a factory alternator gauge. If you have one, you MUST disable it by cutting the large gauge yellow [or maybe red?] wire that runs through your factory alternator Amp gauge in the dash. This wire has all the current from the alternator running through it, and cannot handle the power from the 3G.
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3G Wiring Help Needed
