Field Circuit Test

Turn ignition to "ON", but do not start engine. Check voltage at slip ring by touching positive probe of voltmeter to field terminal (EX) with regulator attaching screws removed. See Fig 1.

Fig 1: Checking Field Circuit (Regulator Wire Connected) Voltage should not exceed 2 volts.
If voltmeter reads more than 2 volts, field circuit is defective. Examine brushes, brush leads and holder. Replace brushes if shorter than .15" (4 mm). If voltmeter reads zero (0) volts, check connections to regulator, ignition switch and indicator lamp.
Check regulator circuit by removing Green lead from field terminal (EX) and measuring voltage across field windings. See Fig 2. 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 2: Checking Regulator Circuit with Voltmeter Green wire must be removed from field terminal.
Turn ignition switch to "ON" position, and run engine faster than idle speed. If incorrect readings were experienced 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 3.

Fig 3: Checking Field Circuit with an Ammeter Use field rheostat in series with ammeter.
Ammeter should read 1-1.5 amps. If ammeter registers less than 1 amp, recheck brushes, leads and slip rings.