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HOMESERVICE MANUALSOLDSMOBILE2004BRAVADA AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 33 (HVAC SYSTEMS - MANUAL)SYSTEM TESTSVACUUM CONTROL SYSTEM
2004 Oldsmobile Bravada AWD

Vacuum Control System

2004 Oldsmobile Bravada AWDSECTION Vacuum Control System
WARNING: This page is about a different car, the 2002 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Check for TEST A: AIR DELIVERY IMPROPER  under SYMPTOM TESTS, before proceeding with the following test.
  1. Start engine and let idle. Turn blower motor fan on and select an air outlet mode. If air flows out of selected HVAC outlet ducts, go to step  3. If air does not flow out of selected HVAC outlet ducts, go to next step.
  2. If system performance concern includes air discharging from correct ducts, then changes during higher engine RPM, go to step  7. If system performance concern is not as described, go to next step.
  3. Start engine and cycle HVAC control unit through all modes. If air comes out of selected outlet ducts, go to step  18. If air does not comes out of selected outlet ducts, go to next step.
  4. With engine running, using a vacuum gauge, record vacuum at manifold vacuum port that supplies vacuum to HVAC vacuum control module. If there is engine vacuum present, go to step  6. If engine vacuum is not present, go to next step.
  5. Repair no vacuum condition. When repair is complete, go to step  18.
  6. Using a vacuum gauge, measure vacuum at vacuum supply line at HVAC vacuum control module. If vacuum measured is equal to engine vacuum, go to step  11. If vacuum measured is not equal to engine vacuum, go to step  8.
  7. Disconnect vacuum supply line from HVAC vacuum control module. Connect vacuum gauge to vacuum supply line, restart engine and turn engine off. If system loses vacuum after turning engine off, go to next step. If system does not lose vacuum after turning engine off, go to step  11.
  8. Check for leaking or collapsed vacuum lines between engine manifold vacuum port and HVAC vacuum control module. If any vacuum lines are leaking, go to next step. If no leaking vacuum lines are found, go to step  10.
  9. Repair or replace leaking vacuum lines as necessary. When repairs are complete, go to step  18.
  10. Replace vacuum reservoir tank. See VACUUM RESERVOIR TANK  under REMOVAL & INSTALLATION. When repair is complete, go to step  18.
  11. Using a hand-held vacuum pump, apply vacuum to each actuator. Each actuator should retract in a smooth motion. Actuator should remain in retracted position and hold vacuum. If all actuators operate as described, go to step  17. If any actuator does not operate as described, go to next step.
  12. Check for leaking or collapsed vacuum lines between actuator and vacuum line at HVAC vacuum control module connector. If any vacuum lines are leaking, go to step  9. If no leaking vacuum lines are found, go to next step.
  13. Disconnect vacuum line from actuator. Using a hand-held vacuum pump, apply vacuum to actuator. If actuator retracts, go to next step. If actuator does not retract, go to step  16.
  14. With actuator disconnected, inspect actuator door for binding. If door moves freely, go to step  16. If door does not move freely, go to next step.
  15. Repair binding actuator door as necessary. When repair is complete, go to step  18.
  16. Replace vacuum actuator. See ACTUATORS  under REMOVAL & INSTALLATION. When repair is complete, go to step  18.
  17. Replace HVAC control assembly. See HVAC CONTROL ASSEMBLY  under REMOVAL & INSTALLATION. When repair is complete, go to next step.
  18. Cycle HVAC controls through all modes to verify proper operation. If condition is corrected, system is okay. If system does not operate correctly, go to step  1.
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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.