Current Output Test
The current output test determines alternator ability to deliver its rated current output.
- Ensure battery is fully charged. Disconnect negative battery cable. Disconnect alternator output wire at alternator battery (BAT) terminal. Using a 0-150 scale DC ammeter, connect positive lead to alternator BAT terminal and negative lead to disconnected alternator output wire. See Fig 1.
- Using a voltmeter (0-18 volts range minimum), connect voltmeter positive lead to disconnected alternator BAT terminal and voltmeter negative lead to good ground. Attach tachometer to engine and reconnect negative battery cable. Connect Variable Carbon Pile Rheostat (C-3950) between battery terminals.
- Ensure carbon pile rheostat is in OFF position before connecting leads. Connect jumper wire between ground and alternator field terminal Dark Green (R3) wire on back of alternator.
- Start engine. Adjust carbon pile rheostat and engine speed until engine speed is 1250 RPM and voltmeter reads 15 volts.
- DO NOT allow voltage to read more than 16 volts. Ammeter should be within specification. See ALTERNATOR SPECIFICATIONS table at end of this article. If amperage is less than specified and alternator output wire resistance is not excessive, replace or repair alternator.
- Turn ignition switch off. Disconnect negative battery cable. Remove test equipment. Reconnect alternator output wire to alternator BAT terminal. Reconnect negative battery cable.