Delco 10si, 12si Alternator Voltage Regulator Testing - zeketheantiquefreak
With a variable voltage DC power source (adjustable from at least 13 to 16 VDC) and a 12VDC bulb socket with pigtails, (or a simple test light) you can easily test these durable voltage regulators. Cutout should occur at ~14.8 VDC.