Mazda MX-5 NA silhouetteMX-5 NA

CHARGING SYSTEM - ALTERNATOR Inspection (Rotor, Stator, Brush)

G-14prose procedure
Continued from G-13

Inspection

Rotor

Rotor Inspection

  1. 1
    Winding damage: (1) Check the resistance between the slip rings with an ohmmeter. Specification: 3.5—4.5Ω/20°C (68°F) (2) If it is not within specification, replace the rotor.
    Hands holding the alternator rotor with both probes of an analog ohmmeter touching the two slip rings to measure winding resistance.
    05U0GX-028
  2. 2
    Ground of field coil: (1) Check for continuity between each slip ring and the core with an ohmmeter. (2) Replace the rotor if there is continuity.
    Rotor held with one ohmmeter probe on a slip ring and one on the rotor core to check for field-coil ground.
    05U0GX-029
  3. 3
    Slip ring surface: If the slip ring surface is rough, use fine sandpaper to repair it.

Stator

Stator Inspection

  1. 1
    Wiring damage: (1) Check for continuity between the stator coil leads with an ohmmeter. (2) Replace the stator if there is no continuity.
    Stator winding being checked with an ohmmeter — probes connected to two of the stator coil lead wires to test continuity.
    05U0GX-030
  2. 2
    Ground of stator coil: (1) Check for no continuity between the stator coil leads and the core with an ohmmeter. (2) Replace the stator if there is continuity.
    Stator being tested for ground; ohmmeter probe on a stator coil lead and the other on the stator core to verify no continuity.
    05U0GX-031

Brush

If the brushes are worn almost to or beyond the limit, replace them.
Rotor winding resistance20°C (68°F)
3.5—4.5Ω
Brush standard length
21.5mm (0.846 in)
Brush minimum length
8.0mm (0.315 in)
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