Alternator Phase Test
Operate alternator at 1000 RPM on a test stand. Do not exceed 1000 RPM or voltage will be high and damage unit. Connect an AC voltmeter or test light of same voltage rating as system (sealed beam headlight with elements in parallel), across each AC terminal in turn. Voltage or lamp brightness should be the same across phases 1-2, 2-3, and 1-3. If there is pronounced difference in voltage or brightness, stator windings are shorted or grounded.