GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Matiz 🢒 Body 🢒 Wiring Systems 🢒 Charging System Test
  1. Perform the generator system test. Refer to Charging System Test .
  2. Replace the generator if it fails that test. Refer to Generator Replacement . If it passes the test, perform the on-vehicle output check which follows.

    3. Object Number: 1223138 Size: SH

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

  3. Attach a digital multimeter (DMM) (a), an ammeter (b), and a carbon pile load (c) to the battery (d) and the generator (e) of the vehicle.

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

  4. With the ignition switch in the OFF position, check and record the battery voltage.
  5. Remove the harness connector from the generator.
  6. Turn the ignition switch to the ON position with the engine not running. Use a DMM to check for voltage in the harness connector L terminal.
  7. The reading should be near the specified battery voltage of 12 volts. If the voltage is too low, check the indicator L terminal circuits for open and grounded circuits causing voltage loss. Correct any open wires, terminal connections, etc., as necessary. Refer to Diagnostic System Check - Engine Electrical .
  8. Attach the generator harness connector.
  9. Run the engine at the moderate idle, and measure the voltage across the battery terminals. The reading should be above that recorded in step 4 but less than 15 volts. If the reading is over 15 volts or below the previous reading, replace the generator. Refer to Generator Replacement .
  10. Run the engine at a moderate idle, and measure the generator amperage output.
  11. Turn ON the carbon pile, and adjust it to obtain the maximum amps while maintaining the battery voltage above 13 volts.
  12. If the reading is within 15 amps of the generator's rating noted on the generator, the generator is good. If not, replace the generator. Refer to Generator Replacement .
  13. 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, check the ground path from the generator housing to the negative battery cable.
  14. Check, clean, tighten, and recheck all of the ground connections.