[Tf175]

Alternator saga restarted .... I have spent the past months replacing /refurbishing exhaust and intake systems, etc . Installed two new Deka 8D batteries and started the engine this morning.  With engine idling at 500 rpm the dash ammeter is negative.  Bring rpm up to about 800 and the ammeter comes alive . At idle the measured voltage is 12.7 +- at battery and at alternator post . I really expected this rebuilt and upgraded alternator to charge at idle , but maybe I'm expecting too much . What do other classic owners see at idle ?
Thanks , Chris