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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 40 (HVAC Systems - Manual) >> Symptom Tests >> Test O: Too Hot In Vehicle >> (3500 HD, Cab & Chassis, Sierra, Silverado)

(3500 HD, Cab & Chassis, Sierra, Silverado)

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  1. Perform SYSTEM OPERATION CHECK  under TROUBLE SHOOTING. Go to next step.
  2. Turn ignition on. Place the blower motor switch in each speed position. Does the blower motor operate at all? If so, go to next step. If not, go to TEST F: BLOWER MOTOR INOPERATIVE .
  3. Does the blower motor operate correctly for each speed position? If so, go to next step. If not, go to TEST H: BLOWER MOTOR MALFUNCTION .
    4. NOTE: The HVAC control assembly is inoperative when the module does not respond to an operator control request.
  4. Is the HVAC control assembly inoperative? If so, go to step  18. If not, go to next step.
    5. NOTE: If the condition does not occur when an A/C request has been made then you must bypass the A/C performance test procedures.
  5. Does the Too Hot in Vehicle concern occur when A/C cooling is desired? If so, go to next step. If not, go to step  8.
    6. NOTE: These actions are the enable criteria for the A/C compressor to operate. Ambient air temperature must be above 38°F (3°C) in order for this A/C compressor test to be run.
  6. Start the engine. Place the blower motor switch in the maximum speed position. Place the A/C request switch in the ON position. Place the air temperature switch in the coldest position. Does the A/C compressor operate? If so, go to next step. If not, go to TEST K: COMPRESSOR CLUTCH DOES NOT ENGAGE .
    7. NOTE: Performing the A/C system performance test ensures that the A/C system is operating properly for further testing.
  7. Perform the A/C system performance test. See A/C SYSTEM PERFORMANCE TEST  under PERFORMANCE TESTS. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
  8. Observe the drive shaft of the air temperature actuator. Adjust the air temperature switch. Does the drive shaft of the air temperature actuator ever rotate? If so, go to next step. If not, go to step  10.
    9. NOTE: If no condition found with all conditions listed then compare door travel to known good vehicle.
  9. Inspect the air temperature door and the air temperature actuator for:
    • Misaligned air temperature actuator.
    • Broken linkages or binding linkages.
    • Broken air temperature door or a binding air temperature door.
    • An obstruction that prevents the air temperature door from operating within the full range of motion.
    • Missing seals to the air temperature door.
    • Misaligned seals to the air temperature door.
    Did you find and correct the condition? If not, go to step  25. If not, check for intermittent and poor connections.
  10. Check the air temperature actuator ignition 3 voltage circuit for an open or for a high resistance. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
  11. Check air temperature actuator the ground circuit for an open. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
  12. Check the air temperature actuator 5-volt reference circuit for a high resistance. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
  13. Check the air temperature door actuator signal circuit for an open or a high resistance. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
  14. Check the air temperature actuator door control circuit for an open or a high resistance. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
    15. NOTE: The voltage will vary between zero-5 volts during normal operation. Ensure to observe the air temperature actuator driveshaft and the volt meter when jumping the control circuit with 5 volt reference and the ground circuits. The air temperature actuator and the HVAC control assembly connectors must be connected during this step.
    NOTE: Ensure the air temperature actuator connector and the HVAC control assembly connectors are connected during this step to avoid misdiagnosis.
  15. Turn ignition on. Backprobe and monitor the voltage from the door signal circuit of the air temperature actuator to ground. Connect a 3-ampere fused jumper between the door control circuit and the 5-volt reference circuit of the air temperature actuator. This drives the actuator to the full cool mode. Remove and reconnect the jumper wire between the air temperature door control and the ground circuit of the air temperature actuator. This drives the actuator to the full hot mode. Does the drive shaft of the air temperature actuator rotate and does the voltage change? If so, go to next step. If not, go to step  20.
    16. NOTE: Ensure the air temperature actuator connector is connected during this step to avoid misdiagnosis.
  16. Backprobe the connector terminal of the air temperature actuator in order to measure the voltage from the door control circuit to ground. Adjust the air temperature switch. Is the voltage measurement near:
    • Zero Volts - Increasing
    • 5 Volts - Decreasing
    • 2.5 Volts - Stationary
    If so, go to next step. If not, go to step  22.
  17. Inspect the air temperature door for a mechanical condition or for a condition that allows excessive travel of the door. After repairs are complete, go to step  25.
  18. Check the HVAC control assembly ignition-3 voltage circuit for an open, for a high resistance, or for a short to ground. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
  19. Check the HVAC control assembly ground circuit for an open. Did you find and correct the condition? If so, go to step  25. If not, go to step  22.
  20. Inspect air temperature actuator harness connector for poor connections. Did you find and correct the condition? If so, go to step  25. If not, go to next step.
  21. Inspect the air temperature actuator, the door, and any attaching linkage for binding or for a condition that prevents drive shaft rotation. Did you find and correct the condition? If so, go to step  25. If not, go to step  23.
  22. Inspect HVAC control assembly harness connector for poor connections. Did you find and correct the condition? If so, go to step  25. If not, go to step  24.
  23. Replace the air temperature actuator. See AIR TEMPERATURE ACTUATOR  under REMOVAL & INSTALLATION. Perform the calibration procedure for the air temperature actuator. After repairs are complete, go to step  25.
  24. Replace the HVAC control assembly. See HVAC CONTROL ASSEMBLY  under REMOVAL & INSTALLATION. Perform the calibration procedure for the air temperature actuator. After repairs are complete, go to next step.
  25. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step  2.
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