Diode Test (On Vehicle)
- Disconnect electric choke (if equipped) and voltage regulator plug. Connect jumper wire between "A" and "F" terminals of voltage regulator wiring plug. Connect voltmeter to battery posts, start and run engine at idle speed, record voltmeter reading.
- Move positive voltmeter lead to "S" terminal of alternator and note voltmeter reading. If meter reads 1/2 of battery voltage, alternator has an open positive diode. If meter reads about 1.0-1.5 volts more than 1/2 battery voltage, alternator has an open negative diode. Reconnect electric choke (if equipped) back into circuit after test is completed.