Alternator: Testing and Inspection

Fig. 1 Connecting voltmeter & ammeter to charging circuit:

1. Disconnect the wire from terminal B of the alternator and connect it to the negative terminal of the ammeter.
2. Connect the test lead from the positive terminal of the ammeter to terminal B of the alternator.
3. Connect the positive lead of the voltmeter to terminal B of the alternator.
4. Connect the negative lead of the voltmeter to ground.

Circuit Test Without Load

1. With the engine running from idling to 2000 rpm, check the reading on the ammeter and voltmeter.

Standard Amperage: Less than 10 amps
Standard Voltage: 13.5 - 15.1 volts at 77° F (25° C)

2. If the voltage reading is greater than spec, replace the IC regulator.

Ground Terminal F:

3. If the voltage reading is less than spec ground terminal F of the alternator as shown, start the engine and check the voltage reading of terminal B.
4. If the voltage reading is greater than spec, replace the IC regulator.
5. If the voltage reading is less than spec, replace the alternator.

Circuit Test Under Load

1. With the engine running at 2000 rpm, turn on the high beam headlights, place the heater fan control on HI, then check the ammeter.

Standard Amperage: More than 30 amps

2. If the ammeter reading is less than 30 amps, replace the alternator.

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