Make Your Own Alternator Tester Cheap & Simple

I am fascinated by three phase power. Not ready to make the modification when all seems to be fine.

My alternator did fail three years ago while on the road. Light came on the dash, dash voltmeter dropped a bit. Continued on a couple hours to the next town in WY. No shop could get me in so I changed it myself. Lifetime warranty from O'Reilly and on down the road I go. IIRC O'Reilly tested the old before selling me a new one.