alternator wiring ????

hi all, just finishing the odd jobs after fitting a disco 200 tdi into my 110 (was a td)
i think i have most of the fiddly bits sorted but i'v come across a difference in the wiring, iv fitted the loom off the td onto the disco engine and the alt wiring is different, my old alt - valeo va 140 has the lucas style 3 wire plug on it and the disco alt - lucas lrb128 has 1 fat brown wire, i skinny browm wire and 1 white wire, i'm guessing that i join the 3 fat browns together and also join the 2 skinny browns,
what about the white one ???? just ignore it
thanks guys
chris

look up the wiring diagrams before yu touch a thing!

i see sparks already

thanks hat man