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Vacuum Control System Diagnostic Test

WARNING: This page is about a different car, the 2002 Oldsmobile Intrigue. However, it is still accessible from the selected car via links, so may be relevant.
  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. See VACUUM DIAGRAMS . 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 control vacuum valve. With vacuum gauge connected to vacuum supply line, start engine, then turn engine off. If A/C system loses vacuum after turning engine off, go to next step. If A/C system does not lose vacuum after turning engine off, go to step  11.
  8. Visually inspect for leaking or collapsed vacuum lines between engine manifold vacuum port and HVAC control vacuum valve. If vacuum lines are leaking, go to next step. If vacuum lines are not leaking, go to step  10.
  9. Repair or replace collapsed or leaking vacuum line. When repair is completed, 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 an external vacuum source, apply vacuum to appropriate vacuum line at HVAC control vacuum valve connector. See VACUUM DIAGRAMS . If actuator retracts, go to step  17. If actuator does not retract, go to next step.
  12. Inspect for leaking or collapsed vacuum lines between actuator and HVAC control vacuum valve connector. If vacuum lines are leaking, go to step  9. If vacuum lines are not leaking, go to next step.
  13. Disconnect vacuum line from actuator. Using an external vacuum source, apply vacuum to actuator. If actuator retracts, go to next step. If actuator does not retract, go to step  16.
  14. With actuator disconnected, visually inspect door for binding. If door moves freely, go to step  16. If door does not move freely, go to next step.
  15. Repair appropriate binding door as necessary. When repair is complete, go to step  18.
  16. Replace faulty 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 step  18.
  18. Cycle HVAC controls through all modes to verify proper operation. If system operates properly, system is okay.
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