Alternator: Testing and Inspection

1. Visually check alternator belt and wiring.
2. Proceed to Step 5. for vehicles not equipped with indicator lamp.
3. Ignition On, engine not running, lamp should be on. If not, disconnect wiring harness at alternator, ground ``L'' terminal lead.
a. Lamp lights, replace or repair alternator.
b. Lamp does not light, locate open circuit between grounding lead and ignition switch.
4. Ignition On, engine running at idle. Lamp should be off. If not, disconnect wiring harness at alternator.
a. If lamp goes out, replace or repair alternator.
b. If lamp stays on, check for grounded ``L'' terminal in wiring harness.
5. Disconnect wiring harness from alternator.
a. Ignition switch on, engine not running, connect voltmeter from ground to terminal ``L'' in wiring harness, and to ``I'' terminal. If used. Wiring harness may connect to either ``I'' or ``L'' terminal or both.
b. Zero reading indicates open circuit between terminal and battery. Repair as necessary.
c. Reconnect wiring harness to alternator, operate engine at moderate speed with all accessories Off.
d. Measure voltage across battery. If voltage is above 16.0 volts, repair or replace alternator as necessary.
6. Connect ammeter at alternator output terminal. Turn on accessories, load battery with carbon pile to obtain maximum amperage output. Maintain voltage at 13.0 or above.
a. If within 15 amperes of rated output, alternator is good.
b. If not within 15 amperes of rated output, repair or replace alternator as necessary.