Alt electrical problem

[USA69Z]

Guys , im having a headache with my truck electrics.. my battery died the other day (3 months old) so i replaced it under warranty and thought my alternator was faulty.. so i replaced it ,, so i have a new battery and alternator fitted and under a test it isnt charging? so i took the truck to an auto electrician and they bench tested it and it came in at 14volts? so i have re fitted and it dosn't charge when fitted .? is there something i can check? 3 wire hookup.. 1 big red wire to post and a brown to 'f' (field) and pinky red to 'r' .. does the charge light on the dash have anything to do with the charging circut? or any ideas?

1970 - i have a int reg alt and wired to suit. hei dissy ..

thanx, Gav