Alternator Output Wire Votage Drop Test

This test judges whether or not the wiring between alternator "B" terminal and battery positive terminal is sound by voltage drop method.

Fig. 1 Voltage Drop Test:

1. Refer to Fig. 1 when preparing the charging system as follows:
a. Turn ignition switch to Off position.
b. disconnect battery ground cable.
c. Disconnect alternator output lead from alternator terminal "B".
d. Connect a 0-100 DC ammeter in series to terminal "B" and the disconnected output lead. Connect positive lead of meter to terminal "B" and negative lead to disconnected output wire.
e. Connect positive lead of a digital voltmeter to alternator terminal "B" and negative lead to battery positive terminal.
f. Connect battery ground cable.
2. Start engine.
3. Turn headlights and small lights On or Off and adjust engine speed so that ammeter reads 20 amps and read value on voltmeter under this condition.
4. If voltmeter indicates maximum value of 0.2 volts, system is operating correctly.
5. If voltmeter indicates a value that is larger than the standard value, poor wiring is suspected between terminal "B" and battery positive terminal.
6. After completion of test, set engine speed at idle, turn Off lights and ignition switch.
7. Disconnect battery ground.
8. Disconnect ammeter and voltmeter then reconnect alternator output wire and connect battery ground cable.