Envoy, Rainer, Trailblazer 2006-2007

Alternator

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Diagnosis & Testing



  1. Check drive belt(s) for wear and tension. Check wiring for obvious damage.
  2.  
  3. Go to Step 7 for vehicles without a charge indicator lamp.
  4.  
  5. With the ignition switch ON and the engine stopped, the lamp should be ON. If not, detach the wiring harness at the generator and ground the -L'' terminal lead.
  6.  
  7. If the lamp illuminates, replace the alternator. If the lamp does not illuminate, locate the open circuit between the grounding lead and the ignition switch. Check the lamp, it may be open.
  8.  
  9. With the ignition switch ON and the engine running at moderate speed, the lamp should be OFF. If not, stop the engine, then turn the switch ON and detach the wiring harness at the alternator.
  10.  
  11. If the lamp goes out, replace the alternator. If the lamp stays ON, check for a grounded -L'' terminal wire in the harness.

    Click image to see an enlarged view

    Fig. Proper connections for alternator testing

  12.  
  13. Determine if the battery is undercharged or overcharged.

    An undercharged battery is evidenced by slow cranking or a dark hydrometer.
     
    An overcharged battery is evidenced by excessive spewing of electrolyte from the vents.
     

  14.  
  15. Detach the wiring harness connector from the alternator.
  16.  
  17. With the ignition switch ON , and the engine not running, connect a voltmeter from ground to the -L'' terminal in the wiring harness, and to the -I'' terminal, if used.
  18.  
  19. A zero reading indicates an open circuit between the terminal and the battery. Repair the circuit as necessary.
  20.  
  21. Attach the harness connector to the alternator and run the engine at moderate speed with accessories OFF.
  22.  
  23. Measure the voltage across the battery. If above 16 volts, replace the alternator.
  24.  
  25. Connect an ammeter at the alternator output terminal, run the engine at moderate speed, turn ON all the accessories and load the battery with a carbon pile to obtain maximum amperage. Maintain voltage at 13 volts or above.
  26.  
  27. If the output is within 15 amps of the rated output of the alternator (stamped on the alternator case), the alternator is good. If the output is not within 15 amps, replace the alternator.
  28.  

Removal & Installation



4.2L Engines
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Remove or disconnect the following:

    Negative battery cable
     
    Accessory belt
     
    Positive battery cable nut from the generator
     
    A/C line mounting bracket bolt at the engine lift hook
     
    Right engine lift hook bolts
     
    Engine lift hook
     
    Mounting bolts
     
    Alternator

    Click image to see an enlarged view

    Fig. Alternator mounting-4.2L engine

     

  4.  

To install:

  1. Install or connect the following:

    Alternator and loosely install the mounting blots
     
    Tighten the alternator mounting bolts to 37 ft. lbs. (50 Nm)
     
    Positive battery cable and secure with the nut; tighten the nut to 80 inch lbs. (9 Nm)
     
    Engine lift hook and bolts; tighten the bolts to 37 ft. lbs. (50 Nm)
     
    A/C line bracket to the lift hook, then tighten the retaining bolt to 89 inch lbs. (10 Nm)
     
    Accessory belt
     
    Negative battery cable
     

  2.  

5.3L & 6.0L Engines
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Remove or disconnect the following:

    Negative battery cable
     
    Accessory belt
     
    Electrical connector
     
    Terminal stud nut, after sliding boot down
     
    Alternator cable
     
    Mounting bolts
     
    Alternator

    Click image to see an enlarged view

    Fig. Alternator mounting-5.3L engine

     

  4.  

To install:

  1. Install or connect the following:

    Alternator and loosely install the mounting bolts
     
    Tighten the bolts to 37 ft. lbs. (50 Nm)
     
    Alternator cable
     
    Terminal stud nut and tighten to 80 inch lbs. (9 Nm)
     
    Boot back over terminal stud
     
    Electrical connector
     
    Accessory belt
     
    Negative battery cable
     

  2.  

 
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