DESCRIPTION
Hitachi alternators are conventional 3-phase, self-rectifying alternators. Three positive and 3 negative diodes are used to rectify current. All models are equipped with Integrated Circuit (IC) voltage regulators.
The IC voltage regulator consists of integrated circuits using transistors. These transistors control current flow to alternator rotor, thus maintaining alternator output voltage at a constant value.
On the charge indicator light circuit, a diode monitors alternating voltage at the stator. When monitored voltage and charging voltage are equal, the charge indicator light is turned off.
Exploded View of Typical Hitachi Alternator. Scheme 1
Alternator Test
- Ensure battery is fully charged prior to beginning test. Turn ignition on and check charge indicator light on instrument panel. If light comes on, go to step 3). If light is off, disconnect alternator connector and ground "L" wire.
- If light remains off, replace indicator bulb and retest. If light comes on, reconnect alternator and ground "F" terminal by using a wire. (Scheme 2) If light is off, repair alternator. If light is on, replace IC regulator.
- Start and run engine at idle. If light is dim, flickers or remains on (bright), repair alternator. If light goes off, run engine at 1500 RPM and turn on headlights. If charge indicator light goes off, go to step 5).
- If charge indicator light is dim, idle engine and measure voltage between terminals "B" (positive) and "L" (negative). If less than.5 volt, alternator is okay. If more than.5 volt, repair alternator.
- Run engine at 1500 RPM and measure terminal "B" voltage. If more than 15.5 volts, replace IC regulator. If 13-15 volts, idle engine and check indicator light. If off, system is okay. If on, repair alternator.
Nissan Alternator Test. Scheme 2
Rotor
Connect ohmmeter to rotor slip rings. If reading is 4-5 ohms rotor continuity is satisfactory. If not, rotor is defective. Connect ohmmeter between one slip ring and rotor core. If continuity exists, replace rotor assembly.
Stator
Using ohmmeter, check continuity between stator core leads. If there is no continuity between leads, replace stator. Connect ohmmeter between stator core and to each stator lead. If there is no continuity, stator is good. If continuity exists, stator is grounded and must be replaced.
Diodes
Using an ohmmeter, check continuity on all diodes in both directions. Current should flow in one direction only. If current flows in both directions, diode is shorted. If current does not flow in either direction, diode is open. If any diode is defective, replace entire diode assembly.
Brushes
- Inspect brushes for freedom of movement in holder. Clean brush holder if necessary. Check brushes for cracks and wear. Check brush springs for corrosion or damage.
- Replace brush holder assembly if brush wear has reached limit line on brush.
- Test brush holder to ensure no continuity exists between holder and brush. Protrusion of NEW brushes must be .41-.45" (10-11 mm).
