Alternator In-Vehicle Testing

Disconnect battery and alternator before arc welding on vehicle.




1. Connect voltmeter across battery terminals and read battery voltage.
2. Start engine and raise engine speed until voltmeter needle stabilizes. Voltage reading should be 12.5-15 volts within 10 minutes.
3. Return engine to idle and turn on all accessories.
4. Gradually increase engine speed until voltage reading stabilizes. Voltage reading should be 12.5-15 volts within 10 minutes.
5. If voltage readings are within specifications, charging system is satisfactory. If readings are consistently below 12.5 volts, inspect charging system and repair as needed. If reading is consistently above 15 volts, check for defective regulator.