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Home >> Pontiac >> 2001 >> Aztek Base, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 206 (Heater Systems) >> Performance Tests >> Heater Performance Test (Front System)
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Heater Performance Test (Front System)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, 2002 Chevrolet RV Cutaway, and 2002 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
NOTE: The manufacturer does not separate testing by "heater only" or "air conditioned" vehicles. References to air conditioning operations or repairs may not apply to vehicles without air conditioning. References to some components also may not apply to vehicles without air conditioning.
NOTE: Definition: Heating system performance.
  1. Were you sent here from TROUBLE SHOOTING? If so, go to next step. If not, see TROUBLE SHOOTING .
  2. Start the engine. Allow the engine to idle. Does the engine reach a normal operating temperature? If so, go to next step. If not, go to step  15.
  3. Allow the engine to idle. Select the warmest temperature setting. Select the minimum blower speed. Select the OFF position for the auxiliary heating system, if equipped. Feel the temperature of the heater inlet and outlet hoses at the hot water bypass valve. Does the inlet heater hose feel warmer than the outlet heater hose? If so, go to step  13. If not, go to next step.
  4. Disconnect the vacuum hose from the hot water bypass valve. Is vacuum being applied to the valve? If so, go to step  14. If not, go to next step.
  5. Remove the hot water bypass valve. See HOT WATER BY-PASS VALVE  under REMOVAL & INSTALLATION. Inspect the hot water bypass valve for the following conditions:
    • Binding
    • Restrictions
    • Damage
    Are any of the listed conditions present? If so, go to step  16. If not, go to next step.
  6. Is the vehicle equipped with Auxiliary Heater (RPO C36)? If so, go to next step. If not, go to step  8.
  7. Inspect the auxiliary coolant bypass valve for the following conditions:
    • Binding
    • Stuck Open
    Is the auxiliary coolant bypass valve stuck open? If so, go to step  17. If not, go to next step.
  8. Install the hot water bypass valve. See HOT WATER BY-PASS VALVE  under REMOVAL & INSTALLATION. After repairs are complete, go to next step.
  9. Allow the engine to idle. Select the FLOOR mode. Select the minimum blower speed. Select the warmest temperature setting. Feel the temperature of the inlet and outlet heater hoses to the heater core. Does the inlet heater hose feel warmer than the outlet heater hose? If so, go to step  13. If not, go to next step.
  10. Install a thermometer into the center I/P PANEL air outlet. Secure a thermometer to the heater core outlet hose. Select the PANEL mode. Select the maximum blower speed. Select the warmest temperature setting. Record the temperature at the center I/P PANEL air outlet and the heater core outlet hose. Compare the recorded temperatures. Are the two temperature readings about equal? If so, go to next step. If not, go to step  12.
  11. Inspect the following areas of the vehicle for cold air leaks:
    • The Cowl
    • The Recirculation Door
    • The HVAC Module Case
    Perform the necessary repairs. After repairs are complete, go to step  19.
  12. Inspect the temperature door operation. Perform any necessary repairs. After repairs are complete, go to step  19.
  13. Turn the engine off. Backflush the heater core. Start the engine and allow to idle. Select the FLOOR mode. Select the minimum blower speed. Select the warmest temperature setting. Feel the temperature of the inlet and outlet heater hoses at the heater core. Does the inlet heater hose feel warmer than the outlet heater hose? If so, go to step  18. If not, go to step  19.
  14. Repair the vacuum condition. After repairs are complete, go to step  19.
  15. Repair the low engine temperature concern. After repairs are complete, go to step  19.
  16. Replace the hot water bypass valve. See HOT WATER BY-PASS VALVE  under REMOVAL & INSTALLATION. After repairs are complete, go to step  19.
  17. Replace the auxiliary coolant bypass valve. See AUXILIARY HOT WATER BY-PASS VALVE  under REMOVAL & INSTALLATION. After repairs are complete, go to step  19.
  18. Replace the heater core. See HEATER CORE  under REMOVAL & INSTALLATION. After repairs are complete, go to step  19.
  19. Operate the system in order to verify the repair. Did you find and correct the condition? If so, system is okay. If not, go to step  2.
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