Nissan 240sx S13 Alternator and Regulator ( Mitsubishi ): overhaul, testing and more
Nissan 240sx S13Conventional 3-phase, self-rectifying Mitsubishi alternator contains 6 diodes (3 positive and 3 negative). Diodes rectify current. Regulator is inside alternator.
ADJUSTMENTS
BELT TENSION
ALTERNATOR BELT ADJUSTMENT
- 240SX: .28-.31 (7-8) Deflection In. (mm)
Deflection is with 22 lbs. (10 kg) pressure applied midway on the longest belt run.
TESTING
ON-VEHICLE TESTING
NOTE: Before testing, ensure alternator wire harness connections are secure, drive belt tension is okay and battery is fully charged. After starting engine, wait at least 30 seconds before measuring voltage. Terminals "B", "E", "L" and "S" are marked on the alternator's rear cover.
Alternator Test
1. Turn ignition on. If charge indicator light on instrument panel comes on, go to step 3).
2. If light is off, disconnect alternator connector (terminals "L" and "S"). Ground terminal "L". If light comes on, repair or replace alternator and/or replace regulator. If light remains off, replace indicator bulb, reconnect alternator connector and retest.
3. Start and run engine at idle. If charge indicator light is dim, flickers or remains on (bright), repair or replace alternator. If light goes off, run engine at 1500 RPM with headlights on. If light comes on, repair or replace alternator.
4. If light remains off, measure voltage at terminal "B" with engine running at 1500 RPM. If more than 15.5 volts are present, replace regulator. If voltage is 13-15 volts, alternator and regulator are okay. Ensure alternator output amperage is as specified.
ALTERNATOR OUTPUT AMPERAGE SPECIFICATIONS
- 240SX
- Output Amps @ RPM: 60 @ 2500/90 @ 5000
BENCH TESTING
Rotor
Connect one ohmmeter lead to each rotor slip ring. If about 2-3 ohms resistance is present, rotor is okay. If about 2-3 ohms resistance is not present, rotor is defective. Connect an ohmmeter lead to any slip ring, and connect remaining lead to rotor core. If continuity exists, replace rotor assembly.
MINIMUM SLIP RING DIAMETER
- 240SX: .87 (22) Diameter In. (mm)
NOTE: To test stator or diodes, separate them by unsoldering connecting wires. Use just enough heat to melt solder. Excess heat will damage diodes.
Stator
Using ohmmeter, check continuity between stator core leads. If continuity is not present between leads, replace stator. Connect one ohmmeter lead to stator core. Connect remaining ohmmeter lead, in turn, to each of the stator leads. If continuity is not present, stator is good. If continuity exists, stator is grounded. Replace stator.
Diodes
Using an ohmmeter, check continuity of all diodes in both directions. Continuity should exist in only one direction. If continuity exists in both directions, diode is shorted. See Fig. 1 . If continuity is not present in either direction, diode is open. If any diode is defective, replace entire diode assembly.
Fig. 1: Testing 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. Ensure brushes are at least .31" (8 mm) long.
OVERHAUL
NOTE: A ring is used to lock outer bearing race in alternator's rear cover. It may be necessary to heat bearing housing to remove cover. Use 200-watt soldering iron to heat housing. DO NOT use heat gun, as it may damage diode. For exploded view of alternator, see Fig. 2 .
Fig. 2: Exploded View Of Typical Mitsubishi Alternator
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Nissan 240sx S13
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