Diode Trio Test

Diode trio assembly with one or more diodes completely opened or shorted will cause reduced alternator output and necessitate alternator disassembly to unsolder diode leads for testing. This test is to check diode assembly for marginal defects which are not affecting alternator output but may cause alternator indicator bulb to glow dimly. Test diode assembly as follows:

1. Connect voltmeter positive lead to alternator output terminal and negative lead to alternator regulator terminal. Start engine and operate at idle speed. Turn on headlights and place blower motor on high speed for approximately two minutes.
   NOTE: This electrical load will heat up diode trio.
2. If voltmeter reading is over 0.6 volts and alternator output was satisfactory in an earlier test, remove diode trio assembly for bench test to determine if diode assembly or solder joints are cause of problem. If meter pulsates, either diode trio, a positive diode or one of soldered connections is beginning to break down under heat and alternator must be disassembled. If voltmeter reading is under 0.6 volts, diode trio assembly is functioning properly.