Generator Output Test

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

1. Install and connect the generator to the test stand as shown in Fig 1. The ground polarity of the generator and the battery must be the same. The carbon pile must be turned off to begin the test. Be sure that the generator BAT terminal is connected to the battery positive terminal (through the ammeter) and that the battery and generator are properly grounded.
Fig 1: Identifying Connections For Generator Output Test
Courtesy of GENERAL MOTORS CORP.
2. Connect a 30 to 500 ohm resistor between the positive battery terminal and the terminal on the generator.
3. Operate the generator through the test stand, increasing speed slowly, and observe the voltage.
4. 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 problems in the regulator.
5. If the voltage is below 16 volts, increase speed and adjust the carbon pile to obtain maximum amperage output Maintain the voltage above 13 volts.
6. If the output is within 15 amperes of the rated out-put, the generator is good.
7. If the output is not within 15 amperes of the rated output, replace the generator.