Voltage @ cruise

Factory 1979 service manual reads:

Ambient temp. near voltage regulator / Voltage range

-20deg. F 14.9v-15.9v
80deg. F 13.9v-14.6v
140deg. F 13.3v-13.9v
above 140 deg.F less than 13.6v

For the 100 amp. alternator, bench testing of the field coil current draw is as follows: isolate the alternator on wood or rubber, connect one field terminal to a fully charged battery, connect one ammeter lead to the other field terminal and the other ammeter lead to the other battery post. Slowly rotate the alternator by hand and you should get 4.75 Amp. to 6 Amp draw @ 12 volts.