alternator not charging on my f250 6.0?

The big one goes to the batt. + and the alt is grounded to the motor , one small wire comes from the ignition to " excite " the regulator , one small wire is to sense the need for voltage and the other may go to the computer , This is my best guess . Wires are color coded don't know why things don't work if they were put back ( soldered ) where they were .

thank you for the information. i got it working and it is charging know the way its suppose too. thanks for replying back to me. other question same truck it was running just fine. i have replace the (hpop) and the discharge tub and( ipr) valve. truck was running like it should. but know it stopped running. i took the (ipr) valve and checked it it looked fine went back in and checked the( hpop) and discharge tub and they all looked like it should. but it wont start? what else can i check that would make it stop running. i looked at he oil filterand checked that the oil was comimg up and it was. so im at a lose dont know what else to check. the parts were from the ford company..

oh be the way i did replace the stand pipes and dummy plugs as well...