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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heater Systems >> Performance Tests >> Heater Performance Test

Heater Performance Test

CAUTION: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
  1. Were you sent here from another test? If so, go to next step. If not, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING. If problem is not found in SYMPTOM DIAGNOSIS, go to next step.
  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  9.
  3. Allow to idle. Select the FLOOR mode. Select the minimum blower speed. Select the maximum temperature setting. Feel the temperature of the inlet and outlet hoses at the heater core. Does the inlet hose feel warmer than the outlet hose? If so, go to step  7. If not, go to next step.
  4. Install a thermometer into the I/P center air outlet. Secure a thermometer to the heater core outlet hose. Select the PANEL mode. Select the maximum blower speed. Select the maximum temperature setting. Record the temperature at the following locations:
    • The I/P Center Air Outlet
    • The Heater Core Outlet Hose

    Compare the recorded temperatures. Are the temperatures similar? If so, go to next step. If not, go to step  6.

  5. Inspect and repair the following areas of the vehicle for cold air leaks:
    • The Cowl
    • The Recirculation Door (If Equipped)
    • The HVAC Module Case
    Perform the necessary repairs. After repairs are complete, go to step  10.
  6. Inspect the temperature door operation. See DIAGNOSTIC SYSTEM CHECK  under TROUBLE SHOOTING. Perform any necessary repairs. After repairs are complete, go to step  10.
  7. Turn the engine off. Backflush the heater core. Start the engine. Select the FLOOR mode. Select the minimum blower speed. Select the maximum temperature setting. Feel the temperature of the inlet and outlet hoses at the heater core. Does the inlet hose feel warmer than the outlet hose? If so, go to next step. If not, go to step  10.
  8. Replace the heater core. See HEATER CORE  under REMOVAL & INSTALLATION. After repairs are complete, go to step  10.
  9. Repair the low engine temperature concern. After repairs, go to next step.
  10. Operate the system in order to verify the repair. Does the system operate correctly? If so, system is okay. If not, go to step  2.
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