Diode Test

Remove rectifier assembly from alternator. Set ohmmeter to X1 scale. Connect one ohmmeter probe to either terminal screw. Connect other probe to each diode lead terminal in turn. Record resistance measurements.
Transpose probes and repeat test. All diodes should have resistance of approximately 6-10 ohms in one direction and no needle movement with probes transposed. Repeat test for other set of diodes, moving first probe to other terminal screw. If measurements are not as specified, replace rectifier assembly.