Alternator: Testing and Inspection

Prior to performing test, check for proper alternator belt tension and proper electrical connections at alternator. Also check battery condition and for blown fuses at fuse panel and engine compartment relay panel.

1. Start engine and allow to reach operating temperature, then stop engine.
2. Disconnect electrical connector from alternator.

Fig. 10 Alternator Electrical Connector Terminal Identification:

3. With ignition switch On, check for battery voltage between ground and alternator connector terminals IG, Fig. 10. If battery voltage is indicated, proceed to step 4. If no voltage is indicated, check for the following:
a. Check for blown fuse in fuse panel.
b. Check for open circuit in black/yellow wire between fuse panel and voltage regulator.
4. Connect voltmeter positive lead to battery positive terminal and negative lead to alternator electrical connector terminal C. With all accessories off, start engine and note voltmeter reading. If battery voltage is indicated, proceed to step 5. If no voltage is indicated, check for the following;
a. Check for an open circuit in white/yellow wire from voltage regulator to Programed Fuel Injection (PFI) electronic control unit.
b. If wiring is satisfactory, PFI electronic control unit may be defective.
5. If battery voltage is indicated, turn on headlamps and note voltmeter reading. If no voltage is now indicated, proceed to step 6. If battery voltage is still indicated, check for the following:
a. Check for short circuit in white/yellow wire from voltage regulator to PFI electronic control unit.
b. If wiring is satisfactory, PFI electronic control unit may be defective.

Fig. 8 Alternator Full Field Access Hole Location. Mitsubishi Units:

Fig. 9 Alternator Full Field Access Hole Location. Nippon Denso Units:

Fig. 11 Alternator Current Output Chart:

6. To further test alternator and regulator, a Sun Vat 40 or other suitable charging system tester should be used. Follow tester manufacturer's instructions for test connections and settings. When performing alternator and regulator tests with tester note the following:
a. When checking alternator output, operate engine at 2000 RPM with engine cooling fan off. Turn on headlamps and rear window defogger. Apply a load to charging system so that voltage drops to no lower than 12 volts. Tester readings should be within 10 amps of readings indicated in Fig. 11. If readings are within specification, charging system is operating properly, refer to CHARGE WARNING LAMP TEST. If readings are not within specification, proceed to step b.
b. Remove protective cover from alternator end cover. Perform full field test by inserting a suitable tool into full field access hole located on end cover, Figs. 8 and 9. When alternator is in full field, system voltage will rise quickly. Do not allow voltage to exceed 18 volts or damage to electrical system may result. Note tester amperage readings with alternator in full field. If readings are still not within specification, replace alternator. If readings are now within specification, refer to step 7.
7. Ensure alternator electrical connector IG terminal indicates battery voltage, Fig. 10. Also check to ensure there is no continuity between alternator connector terminal C and ground. If there is continuity to ground, yellow/white wire may be shorted to ground, PFI electronic control unit maybe faulty or a faulty electric load detector signal to electronic control unit maybe indicated. If checks at alternator electrical connector terminals IG and C are satisfactory, replace voltage regulator.