On Car Testing (11AC)

Check alternator belt and adjust tension. Disconnect battery negative terminal lead. Disconnect the 35-amp output lead from alternator and connect an ammeter between output terminal and output lead. Disconnect leads from alternator field terminals and connect them to battery terminals. Then reconnect battery negative terminal.
Start engine and run up to 4000 alternator RPM. Ammeter should register 40 amps, indicating a good alternator and output lead. If zero or low reading is obtained, check output circuit and wiring by connecting a voltmeter between alternator output terminal and battery positive terminal. Note reading, then transfer voltmeter to alternator frame and battery negative terminal and note this reading. If either reading exceeds 0.5 volt, there is a high resistance is circuit which must be traced and corrected.
If a high resistance is not found, but alternator output is low, remove and examine alternator brush assembly. Retest, and if low output remains, replace or overhaul alternator.
If alternator output is satisfactory, disconnect battery terminal, remove ammeter, and connect alternator output cable to its terminal. Connect battery negative terminal. Switch on ignition and check for proper battery voltage at cable ends by connecting a voltmeter across them. A suitable battery voltage reading indicates field isolating relay circuit and wiring is satisfactory. A low or zero reading indicates a fault in field isolating relay or isolating contacts in ignition switch. See further testing in OVERHAUL procedure.