Frank,
I have not done this swap...only studied it. Assuming you are using a three wire SI alternator, this should work. You don't need a "new" harness, only a few pieces of new wire which you can tape or zip tie into the existing harness to look fine.
Using a new hunk of #10 wire, go from the BATT lug of the alternator to a connection point with the two (?) wires that were on the B terminal of the old external regulator. This must be a good connection! Look at post adjacent to this one in the forum. Cletis shows a picture of a nice junction block.
The DA plug has two wires marked #1 and #2. #1 must go to a source of voltage that is ON when the truck is running. This will excite the field in the alternator and make it charge. This connection can be the RUN position on the key switch, or a coil connection that is BEFORE a ballast resistor, if used. This wire can be small..maybe 14 gauge.
The wire marked #2 must go to a connection somewhere to sense system voltage. It isn't unheard of to run it right over to the BATT lug and attach it. If you wanted, you could hook it to the battery lug on the starter...anywhere as long as it can "see" what the voltage is in the system. This wire tells the alternator to GO or WHOA on its output. 20 million people will pop in hear and tell you where it is best to hook it...hook it up where you want, I'll work fine!
The remaining wires that were attached to the regulator can be taped off and left.
There is the possibility of "feedback", where a voltage generated through the #1 wire will not allow the truck to be shut off. A diode in this line usually solves this problem. I actually think you can purchase a DA pigtail that has a diode already installed...very simple.
So...three wires and you are all set. One #10 and two #14 wires pieces, some zip ties and electrical tape. Maybe a nice dash mounted buss for the main power connection point.
Be sure to save the old regulator, Joker is collecting them for the needy in Mustache, Texas!
Stuart
