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Heating Performance Diagnostic Test

WARNING: This page is about a different car, the 2002 Oldsmobile Intrigue. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
  1. Perform TEST I: TOO COLD IN VEHICLE  test under SYMPTOM TESTS. Go to next step.
  2. Start engine and allow to idle. If engine reaches normal operating temperature, go to next step. If engine does not reach normal operating temperature, go to step  9.
  3. Allow engine to idle. Select FLOOR mode, minimum blower speed, and maximum temperature setting. Feel temperature of inlet and outlet hoses at heater core. If inlet hose feels warmer than outlet hose, go to step  7. If inlet hose does not feel warmer than outlet hose, go to next step.
  4. Install a thermometer into center instrument panel air outlet. Secure thermometer to heater core outlet hose. Select VENT mode, maximum blower speed, and maximum temperature setting. Record temperatures at center instrument panel air outlet and heater core outlet hose. If temperatures are similar, go to next step. If temperatures are not similar, go to step  6.
  5. Inspect cowl, recirculation door and HVAC module case for cold air leaks. If leaks are found, repair as necessary. When repairs are complete, go to step  10.
  6. Check temperature door operation. If problem is found, repair as necessary. When repairs are complete, go to step  10.
  7. Turn engine Off. Backflush heater core. After backflushing is complete and cooling system is filled, start engine and let engine idle until operating temperature is reached. Select FLOOR mode, minimum blower speed, and maximum temperature setting. Feel temperature of inlet and outlet hoses at heater core. If inlet hose feels warmer than outlet hose, go to next step. If inlet hose does not feel warmer than outlet hose, go to step  10.
  8. Replace heater core. See HEATER CORE  under REMOVAL & INSTALLATION. When repairs are complete, go to next step.
  9. Engine is not getting hot enough. Repair low engine temperature concern.
  10. Operate system to verify repair. If system operates correctly, system is okay. If system does not operate correctly, go to step  2.
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