Alternator No-Load Test
- Ensure battery is fully charged and main fusible link is okay. Turn ignition on. Ensure alternator charge indicator light comes on. If charge indicator light comes on, go to step 3). If charge indicator light does not come on, go to next step.
- Unplug alternator connector. Using a jumper wire, connect "L" terminal (harness side) to ground. See Fig 1. If charge indicator light comes on, repair or replace alternator. If charge indicator light does not come on, locate open in "L" terminal circuit between alternator connector and ignition switch.
- Start engine and allow it to idle. If charge indicator light stays on, go to step 4). If charge indicator light flickers on and off, check positive alternator diodes. If charge indicator light goes off, go to step 5).
Courtesy of ISUZU MOTOR CO.
- Turn ignition off. Disconnect alternator connector. Start engine and run at moderate speed. If charge indicator light remains on, check for short to ground in "L" terminal circuit.
- If charge indicator light goes off when engine is started, check charging system voltage at battery. Connect positive voltmeter lead to positive battery terminal and negative lead to ground.
- Increase engine speed to 1500 RPM and check charging system voltage. If charging system voltage is greater than 15.5 volts, replace IC voltage regulator. If charging system voltage is 13.0-15.0 volts, system is okay.