I may have found the cause of the latest ( previous ) f.l. failure: the field wire brush on the alternator lost its screw. I found a replacement screw, and installed it with some blue locktite. Checked function, and the alternator is charging ok. Then I noticed the output terminal stud was rubbing into the heater hose, so I lopped off the end of the stud, beats me why they made it that long anyway.