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HOMESERVICE MANUALSOLDSMOBILE2004BRAVADA AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 41 (HVAC SYSTEMS - MANUAL)PERFORMANCE TESTSHEATING SYSTEM PERFORMANCE
2004 Oldsmobile Bravada AWD

Heating System Performance

2004 Oldsmobile Bravada AWDSECTION Heating System Performance
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.
WARNING: 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 Too Cold in Vehicle? If so, go to next step. If not, go to TEST N: TOO COLD IN VEHICLE  under SYMPTOM TESTS.
  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 I/P center air outlet and 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 cowl, the recirculation door and the heater/vent module case for cold air leaks. Perform the necessary repairs. After the repairs are complete, go to step  10.
  6. On Avalanche, Escalade, Suburban, Tahoe & Yukon:  Start the engine and allow to idle. Depress the mode control button until the LOWER position is displayed. Select the lowest blower speed position. Turn the temperature control knob to the maximum hot position. Check the temperature of the heater inlet and outlet hoses by feel. (The air temperature around the hoses must be at least 85°F (24°C). Does the heater inlet hose feel warm and the heater outlet hose feel cold? Go to step  10.

    On 3500 HD, Cab & Chassis, Sierra & Silverado:  Inspect the temperature door operation. See SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING. Perform any necessary repairs. After repairs are complete, go to step  10.

  7. Turn 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 cause of low engine temperature concern. After the repairs are complete, 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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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.