"Alternator field regulator" fuses keeps blowing

[DanK]

I have a 1999 F-350. I replaced my alternator about three weeks ago. After replacing the alternator, the batteries were charging but the battery light stayed on. I had to plow at the time and evaluated last week. The #6 fuse from the fuse panel under the hood was blown causing the dummy light to go on. I replaced but only lasted 1 day. Keeps blowing. Any ideas where to look?