Subaru Coupes/Sedans/Wagons 1985-1996 Repair Guide

Alternator

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TESTING



See Figure 1

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Fig. Fig. 1: Schematic for testing the alternator

Measuring Regulated Voltage

See Figure 1

  1. Make sure the battery is firmly connected and fully charged.
  2.  
  3. Refer to the diagram, and open switch SW1 while closing switch SW2.
  4.  
  5. Turn the alternator at 5000 rpm and record the voltage.
  6.  
  7. If the alternator is functioning correctly, the voltage should be between 14.3-14.8 volts.
  8.  

Measuring Output Current

See Figure 1

  1. Refer to the diagram, and set the variable resistor to its minimum resistance.
  2.  
  3. Close switches SW1 and SW2.
  4.  
  5. Turn the alternator while keeping the voltage constant by adjusting the variable resistor. Measure the current level at 1250, 2500 and 5000 rpm. If the alternator is functioning correctly, at 1250 rpm, the alternator should be producing at least 18 amps of current. At 2500 rpm, the unit should produce at least 49 amps, and at 5000 rpm, the alternator should produce at least 58 amps of current.
  6.  

Alternator Speed at 13.5 Volts

See Figure 1

  1. Refer to the diagram, and open switch SW1 while closing switch SW2.
  2.  
  3. Slowly raise the alternator speed and record the voltage level.
  4.  
  5. If the alternator is functioning correctly, at 900 rpm, the voltage should be 13.5 volts.
  6.  

REMOVAL & INSTALLATION



See Figures 2, 3 and 4

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Fig. Fig. 2: Unfasten the power wire and indicator light wire from the back of the alternator-1.8L engine shown



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Fig. Fig. 3: Remove the adjusting bolt and bracket, as well as the lower retaining nut and bolt



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Fig. Fig. 4: Lift the alternator out of the engine compartment

  1. Disconnect the negative battery cable.
  2.  
  3. Label and disconnect the alternator electrical wiring harness and battery cable.
  4.  
  5. Loosen the belt tension bracket adjusting bolt at the top of the alternator. Loosen the lower retaining bolt at the base of the alternator. Push the alternator in and remove the accessory drive belt.
  6.  
  7. Remove the alternator adjusting bolt followed by the lower retaining bolt.
  8.  
  9. Remove the alternator from the engine compartment.
  10.  

Now is a good time to inspect the drive belt for wear, replace if necessary.

To install:
  1. Install the alternator on the engine and insert the lower retaining bolt loosely. Attach the bracket and adjusting bolt to the top of the alternator.
  2.  
  3. Install the accessory drive belt and tension. Tighten all bolts securely.
  4.  
  5. Connect the alternator electrical wiring harness and battery cable.
  6.  
  7. Connect the negative battery cable. Start the engine and check the alternator for proper operation.
  8.  

BRUSH REPLACEMENT



See Figures 5, 6, 7, 8, 9 and 10

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Fig. Fig. 5: Disassembled alternator-1.2L engine



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Fig. Fig. 6: Disassembled alternator-1.6L and 1.8L engines



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Fig. Fig. 7: Disassembled alternator-2.2L and 2.5L engines



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Fig. Fig. 8: Disassembled alternator-2.7L engine



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Fig. Fig. 9: Disassembled alternator-3.3L engine



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Fig. Fig. 10: Alternator brush wear limit marks

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the alternator from the engine.
  4.  
  5. Remove the through-bolts from the alternator.
  6.  
  7. Detach the front cover with the rotor from the rear cover with the stator by lightly tapping on the front cover with a plastic hammer.
  8.  
  9. Separate the brush assembly from the rear cover by removing the nuts on the rear cover.
  10.  
  11. As required, disconnect the brush and diode assemblies as well as the IC regulator from the stator coil lead wires using a soldering iron.
  12.  

To install:
  1. Inspect the movement of the brush. If the movement is not smooth, check the brush holder and clean it.
  2.  
  3. Check the brush for wear. If worn beyond the wear marks located on the brushes, replace the brush assembly.
  4.  
  5. Install the brush assembly, diode assembly and IC regulator into the rear cover. Solder the wires as required.
  6.  

Soldering should be done quickly as to not damage the diodes.

  1. Push the brushes into their holders and insert a wire into the back of the alternator to hold the brushes in place. An unfolded paper clip works good.
  2.  
  3. Tighten the diode assembly and brush assembly retaining nuts to 2-3 ft. lbs. (3-4 Nm).
  4.  
  5. Assemble the front and rear case halves. Tighten the through-bolts to 2-4 ft. lbs. (3-5 Nm).
  6.  

 
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