Alternator Output Testing

1. Connect voltage and amperage meter to the vehicle according to the manufacturer's instructions.

NOTE:
For inductive type ammeter, be sure to clip probe around all of the ground cables.

2. Turn off all accessories and lights. Turn the ignition to the "RUN" position and read the rate of discharge on the ammeter.

3. Start the engine and adjust idle speed to 3000 rpm.

4. Voltage reading should be 13.6-14.4 volts. If readings are excessive, the voltage regulator may be at fault. If readings are insufficient, the voltage regulator or alternator may be at fault.

5. Increase load control to obtain the highest reading on the ammeter scale without dropping voltage below 12 volts.

6. Turn load control off and return engine to idle.

7. Add ammeter readings obtained in steps 2 and 5. This is total alternator output.

8. If total alternator output is within 10% of rated output, the alternator is good.