Not charging with headlights on

OK the alternator is good, and the blue wire is good, supplying 12 v to the field.

Now, Check wiring at the regulator connector

To do that, you now want to hook the wire back up to the alternator which goes to the regulator. This would normally be green, but I see yours is not.

This diagram might help

The wire I had you unhook is the field wire marked green at the bottom.

Now hook that up and UNhook the blue field wire, on the diagram, goes over to the ballast. Take your clip lead and ground the alternator field terminal you just unhooked.

Now go up to the regulator connector, and devise a way to jumper across the two terminals. This might take two people, you can use machine screws, nails, etc

Repeat the run test, IE the alternator should charge full tilt, more with more RPM

If this happens, make doubly sure the regulator is grounded.

"Work" the regulator connector on off several times and examine it for corrosion. Hook everything back up "normal" and see if it charges.

If not, replace the regulator.