Alternator Output Test
To avoid a battery explosion, ensure carbon pile rheostat is OFF before connecting to battery.
- Mount alternator on test stand. Ensure ground polarity of alternator and battery are the same. Connect alternator to a fully charged 12-volt battery. Connect voltmeter, ammeter, carbon pile (in OFF position) and 10-ohm resistor (rated at 6 watts or more) between battery and alternator terminal IG. See Fig 1.
- Slowly increase alternator speed and observe voltmeter reading. If voltage is less than 16 volts, go to step 3). If voltage is uncontrolled and increases to more than 16 volts, rotor field is shorted and/or voltage regulator is defective. See VOLTAGE REGULATOR TEST in this article. A shorted rotor field can cause voltage regulator to become defective.
- If voltage is less than 16 volts, increase speed and adjust carbon pile as required to obtain maximum amperage output. Maintain voltage at 13 volts. If maximum output is within 10 amps of rated output (55 amps), alternator is okay. If maximum output is not within 10 amps of rated output, repair or replace alternator.