Alternator/voltage regulator test
Question regarding testing the output of the alternator and the voltage regulator. I went to take the 66 for a spin and the battery was very low. Car wouldn't start. I jumped the battery and it started right up. I observed the ammeter and it was at zero. Didn't move one way or the other during driving. I then parked it and charged the battery for about 2 hours. I tried starting it the next day and it started immediately with a strong battery. There is no apparent reason for the battery to have discharged and I'm wondering if the alternator is not working or the VR is defective. How would I test each part to determine?