For 1990-2009 cars

This test requires both a fully charged battery and a generator test stand to operate the generator.

1. Make connections as shown, except leave the carbon pile turned off. The ground polarity of the generator and battery must be the same. The battery must be fully charged. Use a 30-500 ohm resistor between the battery and the L terminal.
2. Slowly increase the generator speed and observe the voltage.
3. If the voltage is uncontrolled and increases above 16 volts, the rotor field is shorted, the regulator is not working properly, or both. A shorted rotor field coil can cause repeat regulator failure.
4. If the voltage is below 16 volts, increase speed and turn on and adjust the carbon pile to obtain maximum amperage output. Maintain the voltage above 13 volts.
5. If the output is with 15 amperes of the generators rated output, the generator is good.
6. If the output is not within 15 amperes of the generators rated output, replace the generator.