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Vacuum Control System Check

WARNING: This page is about a different car, the 2002 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start engine. Turn blower motor fan to ON position 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 air discharges out correct ducts at first, but then changes during higher engine RPM, go to step  7. If condition is not as stated, go to next step.
  3. With engine running, cycle HVAC controls through all modes. If air flows out of selected outlet ducts, go to step  18. If air does not flow out of selected outlet ducts, go to next step.
  4. With engine running, take a vacuum reading at manifold vacuum port that supplies vacuum to HVAC vacuum control assembly. If there is engine vacuum, go to step  6. If there is not engine vacuum, go to next step.
  5. Repair no vacuum condition. After repairs are complete, go to step  18.
  6. Take a vacuum reading at vacuum supply line at HVAC vacuum control assembly. If vacuum reading is same as engine vacuum, go to step  11. If vacuum reading is different than engine vacuum, go to step  8.
  7. Disconnect vacuum supply line from HVAC vacuum control assembly. With vacuum gauge connected to vacuum supply line, re-start 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. Inspect for leaking or collapsed vacuum lines between engine manifold vacuum port and HVAC vacuum control assembly. 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. After repairs are complete, go to step  18.
  10. Replace vacuum reservoir tank. See VACUUM TANK  under REMOVAL & INSTALLATION. After replacement, go to step  18.
  11. Using an external vacuum source, apply vacuum to appropriate vacuum line at connector to HVAC vacuum control assembly. 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 connector to HVAC vacuum control assembly. 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. Apply an external vacuum source to actuator. If actuator retracts, go to next step. If actuator does not retract, go to step  16.
  14. With actuator disconnected, inspect door for binding. If door moves freely, go to step  16. If door does not move freely, go to next step.
  15. Repair binding door. See AIR DISTRIBUTION DOORS  under REMOVAL & INSTALLATION. After repairs are complete, go to step  18.
  16. Replace vacuum actuator. See VACUUM VALVE ACTUATORS  under REMOVAL & INSTALLATION. After replacement, go to step  18.
  17. Replace HVAC control assembly. See HVAC CONTROL ASSEMBLY  under REMOVAL & INSTALLATION. After replacement, go to next step.
  18. Cycle HVAC controls through all modes to verify proper operation. If system operates properly, system is okay. If system does not operate properly, go to step  1.
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