Field Circuit Test

Turn ignition on, but do not start engine. Check voltage at slip ring by touching positive probe of voltmeter to field terminal "EX" with voltage regulator removed. See Figure .
If voltmeter reads more than 2 volts, field circuit is defective. Check brushes, brush leads and holder. Replace brushes if shorter than .15" (4.0 mm). If voltmeter reads zero volts, check connections to regulator, ignition switch, and indicator light.
Check regulator circuit by disconnecting Green lead from field terminal "EX" and measuring voltage across field windings. See Fig 1 . Voltage should not exceed 2 volts. If voltage is correct, proceed to OUTPUT VOLTAGE TEST . If 8-12 volts is indicated, alternator is defective.

Fig 1: Checking Regulator Circuit with Voltmeter Green wire must be removed from field terminal.
Start and run engine at fast idle. If incorrect readings were obtained in previous test, retest field circuit by disconnecting regulator from field terminal "EX".
Connect an ammeter between field "EX" terminal and output terminal "B+". Use a field rheostat in series with ammeter. This will prevent damage to ammeter from excessive current flow if field is shorted. See Fig 2 .
Ammeter should read 1.0-1.5 amps. If ammeter reads less than one amp, check brushes, leads, and slip rings.

Fig 2: Checking Field Circuit with an Ammeter Use field rheostat in series with ammeter.