Test Lamp Method

Disassemble alternator and separate wires at "Y" connector of stator. Use a test lamp with a No. 67 (4 cp) bulb and a 12 volt battery. Test each rectifier in turn as follows: Touch outer case of rectifier with one probe and wire in center of rectifier with other probe. Reverse the probes, moving probe from outer case to rectifier wire and probe at rectifier wire to outer case. If lamp lights in one direction, rectifier is good. If lamp does not light in either direction, rectifier is open. If lamp lights in both directions, rectifier is shorted.