GM Bonneville/Eighty Eight/LeSabre 1986-1999

Alternator

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TESTING



Basic alternator TESTING can be done with a voltmeter. The alternator function check must be made with a known good, fully charged battery.

1987-91 Vehicles

See Figure 1

  1. Make the connections as shown in the accompanying illustration. Leave the carbon pile turned off. The ground polarity of the alternator and battery must be the same. The battery must be fully charged. If bypassing the indicator light/voltmeter circuit by leaving the 4-cavity connector detached, use a 9-500 ohm resistor between the battery and the "L" terminal.
  2.  



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Fig. Fig. 1: Alternator TESTING connections

  1. Start the engine and let it idle. Turn all electrical loads OFF, then slowly increase the engine speed to 1,500 rpm. Note the voltage reading.
  2.  
  3. If the voltage increases above 16 volts, replace the alternator.
  4.  
  5. If the voltage is below 16 volts, hold the engine speed at 1,500 rpm and adjust the carbon pile to obtain the maximum amperage output. Maintain the voltage above 13 volts. If the output is within 15 amperes of rated output, the alternator is good. If the output is not within 15 amperes of rated output, replace the alternator.
  6.  

1992-95 Vehicles

  1. Make the connections as shown in the accompanying figure. Leave the carbon pile load turned off. The alternator and battery ground polarity must be the same. Detach the alternator (4-cavity) connector, then connect a fused jumper between the positive battery terminal and the alternator terminal "I".
  2.  
  3. Start the engine, turn all of the electrical loads OFF, then slowly increase the engine speed to about 1,500 rpm. Note the voltage reading.
  4.  
  5. When the voltage is uncontrolled and increases above 16 volts, replace the alternator.
  6.  
  7. When the voltage is below 16 volts, hold the engine speed at 1,500 rpm. Turn on the carbon pile and adjust to obtain maximum amperage output. Maintain the voltage above 13 volts. When the output is within 15 amperes of rated output, the alternator is good. When the output is not within 15 amperes of rated output, replace the alternator.
  8.  

1996-99 Vehicles

To test the alternator on these vehicles, make the connections shown in the figure, then follow the test steps in the accompanying chart.

REMOVAL & INSTALLATION



3.8L (VIN 3, C and L) Engines

See Figures 2 through 6

  1. Disconnect the negative battery cable.
  2.  
  3. Using a suitable breaker bar or ratchet, rotate the tensioner counterclockwise, then remove the serpentine drive belt. For more information regarding serpentine drive belt removal, please refer to General Information & Maintenance of this repair guide.
  4.  
  5. If necessary, remove the fuel rail cover.
  6.  
  7. While supporting the alternator, remove the mounting bolts.
  8.  



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Fig. Fig. 2: Remove the 2 alternator mounting bolts (see arrows)

  1. Tilt the alternator forward, then label and detach the electrical connectors.
  2.  



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Fig. Fig. 3: Tilt the alternator forward to unfasten the electrical connections (see arrows) ...



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Fig. Fig. 4: ... then remove the alternator from the vehicle

  1. Remove the alternator from the vehicle.
  2.  



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Fig. Fig. 5: Exploded view of the alternator mounting - 3.8L (VIN C) engine shown



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Fig. Fig. 6: Alternator-to-engine attachment - 1994 3.8L (VIN L) engine shown; other years similar

To install:
  1. Support the alternator in position, then install the alternator.
  2.  
  3. Install the mounting bolts and tighten to 1 ft. lbs. (11 Nm).
  4.  
  5. Attach the electrical connectors at the back of the alternator. Tighten the alternator output terminal nut to 93 inch lbs. (10.5 Nm) for 1987-92 vehicles, or to 66 inch lbs. (7.5 Nm) for 1993-94 vehicles.
  6.  
  7. If removed, install the fuel rail cover.
  8.  
  9. Install the serpentine drive belt and rotate the tensioner into position.
  10.  
  11. Connect the negative battery cable.
  12.  

3.8L (VIN K) Engines

1995 Vehicles

See Figure 7

  1. Disconnect the negative battery cable.
  2.  
  3. Use a suitable breaker bar or ratchet, rotate the tensioner, then remove the serpentine drive belt. For more information regarding drive belt removal, please refer to General Information & Maintenance of this repair guide.
  4.  
  5. Detach the alternator electrical connections.
  6.  
  7. Remove the two nuts and brackets from the alternator.
  8.  
  9. Unfasten the two bolt and one stud securing the alternator, then remove the alternator from the vehicle.
  10.  



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Fig. Fig. 7: Exploded view of the alternator mounting - 3.8L (VIN K) engine

To install:
  1. Position the alternator in the vehicle. Install the two bolts and one stud to secure the alternator. Tighten to 37 ft. lbs. (50 Nm).
  2.  
  3. Install the bracket and two nuts to the alternator. Tighten the bolts and stud to 37 ft. lbs. (50 Nm).
  4.  
  5. Install the electrical connections. Tighten the alternator output terminal nut to 66 inch lbs. (7.5 Nm).
  6.  
  7. Install the serpentine drive belt, as outlined in General Information & Maintenance of this repair guide.
  8.  
  9. Connect the negative battery cable.
  10.  

1996-99 vehicles

See Figures 8 and 9

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the serpentine drive belt from the alternator.
  4.  
  5. Remove the engine cover.
  6.  
  7. Remove the front alternator support brace.
  8.  
  9. Remove the alternator mounting bolts.
  10.  
  11. Remove the rear pencil brace bolt.
  12.  
  13. Unfasten the output terminal nut.
  14.  
  15. Detach the alternator electrical connector(s).
  16.  
  17. Remove the alternator from the vehicle.
  18.  



Click image to see an enlarged view

Fig. Fig. 8: Exploded view of the alternator and brace mounting - 1997 3.8L (VIN K) engine shown

To install:
  1. Position the alternator in the vehicle.
  2.  
  3. Attach the electrical connection(s) and the output terminal nut. Tighten the nut to 15 ft. lbs. (1 Nm).
  4.  



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Fig. Fig. 9: View of the connections on the rear of the alternator

  1. Install the alternator mounting bolts and tighten to 37 ft. lbs. (50 Nm).
  2.  
  3. Install the front alternator support brace and tighten the retainers to 37 ft. lbs. (50 Nm).
  4.  
  5. Install the rear pencil brace bolt and tighten to 6 ft. lbs. (9 Nm).
  6.  
  7. Install the engine cover.
  8.  
  9. Install the serpentine drive belt.
  10.  
  11. Connect the negative battery cable.
  12.  

3.8L (VIN 1) Supercharged Engines

1992-95 vehicles

See Figures 10 and 11

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the serpentine drive belt from the alternator, as outlined in General Information & Maintenance of this repair guide.
  4.  
  5. Detach the electrical connections from the alternator.
  6.  
  7. Unfasten the alternator mounting bolt and mounting bolt and nut.
  8.  
  9. Remove the alternator from the vehicle.
  10.  



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Fig. Fig. 10: Exploded view of the alternator mounting - 1994 supercharged engine; other years similar



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Fig. Fig. 11: Alternator-to-engine attachment - 1995 3.8L (VIN 1) engine shown

To install:
  1. Position the alternator in the vehicle and secure with the mounting nut and bolt. Tighten to 5 ft. lbs. (8 Nm).
  2.  
  3. Install the remaining mounting bolt and tighten to 5 ft. lbs. (8 Nm).
  4.  
  5. Attach the alternator connections. Tighten the output terminal nut to 66 inch lbs. (7.5 Nm).
  6.  
  7. Install the serpentine drive belt.
  8.  
  9. Connect the negative battery cable.
  10.  

1996-99 vehicles

See Figures 9 and 12

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the serpentine drive belt from the alternator.
  4.  
  5. Remove the engine cover.
  6.  
  7. Unfasten the rear pencil brace bolts, then remove the brace.
  8.  
  9. Remove the alternator mounting bolts.
  10.  
  11. Remove the output terminal nut.
  12.  
  13. Detach the alternator electrical connection(s).
  14.  
  15. Remove the alternator from the vehicle.
  16.  



Click image to see an enlarged view

Fig. Fig. 12: Location of the alternator and brace mounting bolts - 1997 supercharged engine shown

To install:
  1. Position the alternator in the vehicle.
  2.  
  3. Attach the electrical connection(s) and install the output terminal nut. Tighten the nut to 15 ft. lbs. (1 Nm).
  4.  
  5. Install the alternator mounting bolt and tighten to 37 ft. lbs. (50 Nm).
  6.  
  7. Install the rear pencil brace bolts and tighten to 6 ft. lbs. (9 Nm).
  8.  
  9. Install the engine cover and serpentine drive belt.
  10.  
  11. Connect the negative battery cable.
  12.  

 
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