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. Disconnect electrical connector from alternator.

Fig. 3 Alternator Electrical Connector Pin Identification. 1989-91 Accord:

Fig. 4 Alternator Electrical Connector Pin Identification. 1989-91 Prelude:

2. With ignition switch On, check for battery voltage between ground and alternator connector terminals IG and S On 1989 models or IG and ground on 1990-91 models, Figs. 3 and 4. If battery voltage is indicated at both terminals, proceed to step 3. If no voltage is indicated, check for the following:
a. On 1989 models, check for open circuits in black/yellow wire between fuse panel and voltage regulator, and white/green wire between engine compartment relay panel and voltage regulator.
b. On 1990-91 models, check for open circuit in white/green wire between engine compartment relay panel and voltage regulator.
c. On all models, check for blown fuse in fuse panel.

Fig. 5 Alternator Current Output Chart. 1989 Accord:

Fig. 6 Alternator Current Output Chart. 1990-91 Accord:

Fig. 7 Alternator Current Output Chart. 1989-91 Prelude:

3. 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. 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 Figs. 5 through 7. 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.

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

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

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 & 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 now within specification, replace voltage regulator. If readings are still not within specification, replace alternator.