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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 >> (Avalanche, Escalade, Suburban, Tahoe & Yukon)

(Avalanche, Escalade, Suburban, Tahoe & Yukon)

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
  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  19. 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  9.
    6. NOTE: If the vehicle has poor A/C performance at idle then there could be an issue with the radiator air baffle assemblies or deflectors.
  6. Inspect the air baffles for proper installation. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
    7. 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.
    NOTE: For A/C compressor operation, ambient air temperature must be above 38°F (3°C).
  7. 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 .
    8. NOTE: Performing the A/C system performance test ensures that the A/C system is operating properly for further testing.
  8. 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  26. If not, go to next step.
  9. Observe the drive shaft of the air temperature actuator. Adjust the air temperature switch. Does the air temperature actuator drive shaft rotate at all? If so, go to next step. If not, go to step  11.
    10. NOTE: If no condition found with all conditions listed then compare door travel to known good vehicle.
  10. Inspect the air temperature door and the air temperature actuator for:
    • Misaligned air temperature actuator.
    • Broken or binding linkages or air temperature door.
    • Obstruction that prevents the air temperature door from operating within its 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 so, go to step  26. If not, check for intermittent and poor connections.
  11. Check the air temperature actuator ignition 3 voltage circuit for an open or a high resistance. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
  12. Check the air temperature actuator ground circuit for an open. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
  13. Check the air temperature actuator 5-volt reference circuit for an open, a high resistance, short to ground, or short to voltage. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
  14. Check the air temperature door actuator air temperature position signal circuit for an open, high resistance, short to ground, or short to voltage. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
  15. Check the air temperature actuator air temperature door control circuit for an open, high resistance, short to ground, or short to voltage. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
    16. 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: The air temperature actuator connector and the HVAC control assembly connector must be connected to correctly perform tests.
  16. Turn ignition on. Backprobe and monitor the voltage from the air temperature door position signal circuit of the air temperature actuator to ground. Connect a 3-ampere fused jumper wire between the air temperature 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 circuit and the ground circuit of the air temperature actuator. This drives the actuator to the full hot mode. Does the air temperature actuator drive shaft rotate and does the voltage change? If so, go to next step. If not, go to step  21.
  17. Backprobe the air temperature actuator connector terminal in order to measure the voltage from the air temperature door control circuit to ground. Adjust the air temperature switch. Does the voltage measure near zero volts when increasing air temperature, near 5 volts decreasing air temperature and near 2.5 volts when stationary? If so, go to next step. If not, go to step  23.
  18. Inspect the air temperature door for a mechanical failure or a condition that allows excessive travel of the door. After repairs are complete, go to step  26.
  19. Check the HVAC control assembly ignition 3 voltage circuit for an open, a high resistance or a short to ground. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
  20. Check HVAC control assembly the ground circuit for an open. Did you find and correct the condition? If so, go to step  26. If not, go to step  23.
  21. Inspect air temperature actuator harness connector for poor connections. Did you find and correct the condition? If so, go to step  26. If not, go to next step.
  22. Inspect the air temperature actuator, door and any attaching linkage for binding or a condition that prevents drive shaft rotation. Did you find and correct the condition? If so, go to step  26. If not, go to step  24.
  23. Inspect HVAC control assembly harness connector for poor connections. Did you find and correct the condition? If so, go to step  26. If not, go to step  25.
  24. Replace the air temperature actuator. See AIR TEMPERATURE ACTUATOR  under REMOVAL & INSTALLATION. Perform the recalibration procedure for the air temperature actuator. After repairs are complete, go to step  26.
    25. NOTE: Perform the recalibration procedure for the HVAC control assembly.
  25. Replace the HVAC control assembly. See HVAC CONTROL ASSEMBLY  under REMOVAL & INSTALLATION. After repairs are complete, go to next step.
  26. 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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