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Diode Test

  1. Start and run engine at 1500 RPM. Record output voltage at terminal "B+". Measure voltage at terminal "D+". Voltage reading should be within .5 volts of battery voltage..
  2. If terminal "D+" voltage is lower, alternator field diodes are defective. If output voltage is high (overcharging) and field diodes are okay, voltage regulator is defective.
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