Alternator

I have a small 10A Black & Decker smart charger which has an "alternator test" function. I think it works as what you are getting at. It looks for excessive ripple on the BATT+ wire, which could indicate a blown diode (of 6) in the alternator output. I think that is why the round-back alternator in my 1965 Newport wasn't charging sufficiently years ago. An easy test is if you measure ~14.3 V at the cigarette lighter with the engine running, your alternator is doing its job. The squareback alternator in my 1982 Dodge Aries (same as 1970's A's) kept melting the 3 positive output diodes every year almost like clockwork. I learned to peer in the rectangular slots and if I saw them missing I knew it was time to replace them again. I suspect they didn't get enough cooling on their floating bar in that transverse engine application. By cutting cooling slots in that bar, I could get them to last 2 years.