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Alternator

TESTING

A voltmeter and ammeter are necessary for testing.

Fig. 1: Alternator, voltmeter and ammeter test connections

  1. Make sure the battery terminals are not loose or corroded. Check the fusible link for continuity.
  2. Inspect the drive belt for excessive wear. Check the drive belt tension. If necessary adjust the drive belt.
  3. Check the following fuses for continuity: ENGINE, CHARGE, IGN fuses.
  4. Visually check alternator wiring and listen for abnormal noises.
  5. Check that the discharge warning light comes ON when the ignition switch is turned ON. Start the engine. Check that the warning light goes out.
  6. Check the charging circuit WITHOUT A LOAD.
    1. Disconnect the wire from terminal B of the alternator and attach it to the negative lead of the ammeter.
    2. Connect the positive lead of the ammeter to terminal B of the alternator.
    3. Connect the positive lead of the voltmeter to terminal B of the alternator.
    4. Ground the negative lead of the voltmeter.
    5. To check the charging circuit, run the engine from idle to 2000 rpms and check the reading on the ammeter and voltmeter. Standard amperage is 10 amps or less. Standard voltage is as follows:
      • 77°F (25°C) — 14.0–15.0 volts
      • 239°F (115°C) — 13.5–14.3 volts
    6. If the voltmeter reading is more than standard voltage, replace the voltage regulator. If the voltmeter reading is less than standard, check the alternator.
  7. Check the charging circuit WITH A LOAD.
    1. With the engine running at 2000 rpm, turn on high beams and heater fan to HI.
    2. Check the standard amperage, it should be 30 amps or more. If the ammeter is less than standard, replace the alternator.
  8. Replace the necessary parts. Recheck the charging system.

    NOTE: If a battery is fully charged, sometimes the indication will be less than 30 amps.

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