Replacing externally regulated alternator with one-wire internally regulated alternator

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mkrazy127

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Joined
Sep 16, 2022
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Location
Burlington, KY
My Car
64.5 Mustang coupe - 289 4bbl.
I am not a wiring expert and have been researching replacing the old externally regulated alternator with an internal one-wire alternator. I have a powermaster 1-wire alternator.

When you read everything online for this, most say just remove the old external regulator and then run a heavy gauge wire from the B+ on the new alternator to either directly to the Battery or the battery side of the starter relay. What doesn't make sense to me is how power will be supplied to the rest of the car. If you look at the picture above, the wires coming from the current regulator are marked with a red arrow. Notice the heavy wire from the current setup goes to a junction (horn relay?) mounted on the fender between the battery and starter relay. The other heavy wire I'm guessing goes to the fuse box, so if I remove that wire, nothing will work. If I take and run the B+ from the new alternator to this junction then how will the battery get charged? My thought is that I need to run a 4g or 6g wire to a 100 amp fuse then from that fuse, run a wire to the both the Battery (or B+ side of stater relay) and that junction (horn relay?).

Next question is with the two wires I have circled - are those for the ALT gauge? Is there a way to still have that function? Most things I've read say to just install a volt meter.

The green arrow is pointing to the connector that went to the external regulator. The wires laying on top of the shock tower were what came off of the old alternator.

Thanks for any help!!
 

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Two thick wires go to that junction box: one from the alternator and one from the main headlight harness. Your 1 wire alternator simply replaces the one thick wire from the alternator harness.
The two wires appear to be non-factory; maybe related to the MSD?
 
Two thick wires go to that junction box: one from the alternator and one from the main headlight harness. Your 1 wire alternator simply replaces the one thick wire from the alternator harness.
The two wires appear to be non-factory; maybe related to the MSD?
The wires I'm pointing to all go to the external regulator harness and/or back of the original alternator and 99% sure they are all factory. After looking again, I do see a second heavier yellow wire also attached there to the B+ side of the starter relay, so that might be what is actually charging the battery. Both are fusable links. It would have been a lot easier to figure this out if the original alternator was actually working when I started on this. So I'll try just running the new 4/6 gauge wire from the B+ of the new alternator to the B+ of the starter relay.
 
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