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Eric, that helps. I may just go back to my conversion idea and use the green/red wire as the switched source. I already modified the 10SI case and original bracket. I don't need all the amperage of the 3G Ford alternator and the GM one is only about 20 amps more than my original alternator.
I did a bit more researching and there are true 1 wire GM conversion alternators available that have a self exciting regulator.
So you found your issue. Now trace the green/red back to the cab and figure out where the connection is broken. Most of the time it's from a bad ignition switch.
Matts72, once you correct and get 12 volts to the red/green wire, you're on you way. See the below pictures of my 71' F250 wiring with the 3G. Note the yellow wire is a simple direct to battery connection. I used the battery terminal clamps with multiple ports to keep everything separated and in plain view. Wire loom is on order to dress everything up in the near future.
Note the yellow wire coming off of the alternator directly to the battery.
Red/Green wire goes to new all green wire of the harness. This is the 12 volt ignition source. Unplugged the plug off of the horn relay/field relay. Cut the 2 wires with the green tape to keep 12v from going to the ammeter gauge in the truck. Will convert to volts from amps down the road.
When all else fails, check for broken wires for the 37th time. Grn/red wire was hacked into by previous owner (my dad) and the connection came loose. It's charging now!
