For 1990-2009 cars

1. Perform the generator system test.
2. Replace the generator if it fails the test. Refer to Generator Replacement .
3. If the generator passes the test, perform the on-vehicle output test which follows.

Important: Always inspect the generator for output before assuming that a grounded L terminal circuit has damaged the regulator.

4. Attach a digital multimeter, an ammeter, and a carbon pile load to the vehicle.

Important: Be sure the vehicle battery is fully charged, and the carbon pile load is turned OFF.

5. With the ignition switch in the off position, inspect and record the battery voltage.
6. Remove the harness connector from the generator.
7. Turn the ignition switch to the RUN position with the engine not running.
8. Use a digital multimeter in order to check for voltage in the harness connector L terminal. The reading should be near the specified battery voltage of 12 volts.
9. If the voltage is too low, inspect the indicator L terminal circuits for open and grounded circuits causing voltage loss. Correct any open wires, terminal connections, etc., as necessary. Refer to Charging System Description and Operation .
10. Attach the generator harness connector.
11. Run the engine at a moderate idle, and measure the voltage across the battery terminals. The reading should be above that recorded in step 15 but less than 16 volts. If the reading is over 16 volts or below the previous reading, replace the generator. Refer to Generator Replacement .
12. Run the engine at a moderate idle, and measure the generator amperage output.
13. Turn ON the carbon pile, and adjust the carbon pile in order to obtain the maximum amps while maintaining the battery voltage above 13 volts. If the reading is within 15 amps of the generator rating listed on the generator, the generator is good. If not, replace the generator. Refer to Generator Replacement .
14. With the generator operating at the maximum output, measure the voltage between the generator housing and the battery negative terminal. The voltage drop should be 0.5 volt or less. If the voltage drop is more than 0.5 volt, inspect the ground path from the generator housing to the negative battery cable.
15. Inspect, clean, tighten, and reinspect all of the ground connections.