Charging System: Testing and Inspection

Fig. 12 Alternator Charging Voltage Test Connection. Battery Voltage Sensing Type Alternator:

1. With ignition switch in the OFF position, disconnect battery ground cable and connect a digital voltmeter between alternator S terminal and ground.
2. Disconnect alternator output wire from alternator B terminal, then connect a DC ammeter in series between the B terminal and the disconnected output wire. Connect positive lead of ammeter to B terminal. Connect negative lead to the disconnected output wire.
3. Install engine tachometer and reconnect battery ground cable.
4. Place ignition switch in the ON position and note voltmeter. The reading should equal battery voltage. If reading is 0, check for an open circuit in the wire between alternator S terminal and battery positive terminal or a blown fusible link.
5. Start engine, keeping all accessories and lights OFF. Run engine at a constant 2500 RPM and read voltmeter when alternator output current drops to 10 amps or less.