Test D: Generator Noise Diagnosis

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test D: Generator Noise Diagnosis
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  1. Test generator for proper operation. See TEST A: CHARGING SYSTEM TEST  . If generator is operating properly, go to next step. If generator is not operating properly, go to step  11 .
  2. Start engine. Verify that generator noise can be heard. Turn ignition switch to OFF position. Disconnect 3-pin harness connector from generator. Start engine. Listen for generator noise. If noise has not stopped, go to next step. If noise has stopped, go to step  11 .
  3. Turn engine off. Remove drive belt. Spin generator pulley by hand. If pulley rotates smoothly and no noise is present, go to next step. If pulley rotates roughly and/or noise is present, go to step  11 .
  4. Inspect pulley for looseness, or loose pulley nut. If pulley and nut are okay, go to next step. If pulley and/or nut is loose, go to step  11 .
  5. Loosen all generator mounting bolts. Tighten generator mounting bolts to specification. See TORQUE SPECIFICATIONS  . Install drive belt. Start engine and listen for noise. If noise is still present, go to next step. If noise has decreased or stopped, system is okay.
  6. Check for stretched generator harness connectors, hoses or other equipment rubbing on generator. If problem exists, go to next step. If no problem exists, go to step  8 .
  7. Reroute electrical connections, hoses, etc., away from generator. Start engine and listen for noises. If noise is still present, go to next step. If noise has decreased or stopped, system is okay.
  8. Check drive belt for proper tension. If drive belt is loose, go to next step. If drive belt is okay, go to step  10 .
  9. Replace drive belt tensioner. Start engine and listen for noise. If noise has decreased or stopped, system is okay. If noise is still present, go to step  11 .
  10. Check comparable vehicle for similar noise. If noise is not present in similar vehicle, go to next step. If noise is present in similar vehicle, system is okay.
  11. If no definite generator problems were found, ensure all other possible sources of noise are eliminated. If all possibilities have been eliminated, replace generator. See GENERATOR  under REMOVAL & INSTALLATION. After repairs are made, go to next step.
  12. Operate system to verify repair. If condition is corrected, system is okay. If condition was not found and corrected, go to step  2 .
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.