Alternator Alternating current question

Yes, engine stopped, of course no AC, and the ammeter inserted "in line". There can still be DC leakage through the diodes from the battery. But there wasn't. There are no shorts anywhere in the car, I went around and checked everything.

Now it turns out the whole ripple thing was a complete fluke. The result of using "el cheapo" VOMs (two different ones), but it turns out they were not "True RMS". The NON-True RMS meters make the assumption that the AC is a nice sine wave of less that 450 Hz and calculate "RMS" on that assumption which of course is totally wrong since the ripple coming from the diode bridge is nothing like a sine wave. The resulting measurement gave an outrageous value of 33 (!!??) volts of AC, which was the clue that something was wrong there because 33 volts would have burned a few things in the car, but that of course didn't happen. The fact that two different meters of different makes gave the same value is what befuddled me. Not all of us can afford a Fluke I guess.

The real ripple turned out to be 0.57 volts. Slightly higher than the recommended 0.5 max but not outrageous (funny thing I afterwards read somewhere that for the 66 Barracuda there could be as much as 2 volts with no ill effects).

The whole thing started because I noticed that the cabin lights were flickering at low RPMs (idling). Which made me think there might be a higher ripple in the alternator, which led to the fluke measurement.....

Moral of the story : use better equipment if you can, and don't believe everything you see without a lot of thinking first.