When they tested the alternator they would haev strapped it to a bench, speed it up by some sort of belt and excuited it to get it charging with a 12 volt power source. I reckon that your alternator isnt getting excited from its ignition wire power source and charging because it that. I wired one up not too long ago but I cant remember the wire colours. A 1ggze alternator has the same permanent live and ignition wire colours as a ra28.