All Models
- Measure resistance, using suitable ohmmeter, across "F" and "E" terminals (rotor coil resistance). Rotor coil circuit is normal if resistance is 4 ohms. If resistance is higher than 4 ohms, there is poor contact between brushes and commutator. If no continuity exists between "F" and "E" terminals, there is either an open rotor coil circuit, brush sticking, or a broken lead wire. If resistance is less than 4 ohms, it indicates rotor coil layer short or grounded circuit.
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NOTE: The following test will not indicate a open stare of the diodes. Tester will indicate a continuity regardless of diode conditions if tester leads are connected to the terminals with polarities reversed.
Connect positive lead of tester to alternator "N" terminal and tester negative lead to alternator "A" terminal. If continuity is observed on the tester, there exists one or more shorted positive diodes.
- Next, connect tester positive lead to alternator "E" terminal and tester negative lead to alternator "N" terminal. If continuity is present, it indicates that one or more of the negative diodes are shorted.