100amp alternator to xflow cortina. help!

[LJDB 103]

i brought a 100amp alternator for my cortina. the alt is similar to this http://www.ebay.com/itm/CHROME-FORD-MUSTANG-II-5-0L-302-V8-1975-1978-ALTERNATOR-/251244557125 in design. it bolts up perfectly but doesnt seem to charge properly and my warning light is on. i was told to put the battery wire to post with bat on it and the (D+) warning lamp wire to the post that says FLD(field). i read that the field post needs 12v ign which is what the D+ wire has. when i disconnect the D+ wire the light goes out. im not sure if it needs an external reg or i need to wire it differently.

 

 

[BBS XE 160]

The ebay one needs an external regulator so if yours is the same it must to.