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Heating Performance Diagnostic

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
Heating Performance Diagnostic

Step Action Yes No
1 Were you sent here from Too Cold in Vehicle? Go to Step 2  Go to TOO COLD IN VEHICLE in HVAC Systems-Manual or TOO COLD IN VEHICLE in HVAC Systems-Automatic
2
  1. Start the engine.
  2. Allow the engine to idle.
Does the engine reach normal operating temperature?		 Go to Step 3  Go to Step 9 
3
    CAUTION: Refer to MOVING PARTS & HOT SURFACES CAUTION in Cautions and Notices.
  1. Allow the engine to idle.
  2. Select the FLOOR mode.
  3. Select the minimum blower speed.
  4. Select the maximum temperature setting.
  5. Feel the temperature of the inlet and outlet hoses at the heater core.
Does the inlet hose feel warmer than the outlet hose?		 Go to Step 7  Go to Step 4 
4
  1. Install a thermometer into the I/P center air outlet.
  2. Secure a thermometer to the heater core outlet hose.
  3. Select the Panel mode.
  4. Select the maximum blower speed.
  5. Select the maximum temperature setting.
  6. Record the temperature at the following locations:
    • The I/P center air outlet
    • The heater core outlet hose
  7. Compare the recorded temperatures.
Are the temperatures similar?		 Go to Step 5  Go to Step 6 
5
  1. Inspect the following areas of the vehicle for cold air leaks:
    • The cowl
    • The air inlet valve
    • The HVAC module case
  2. Perform any necessary repairs.
Are the repairs complete?		 Go to Step 10  -
6
  1. Inspect the temperature door operation.
  2. Perform any necessary repairs.
Are the repairs complete?		 Go to Step 10  -
7
  1. Turn OFF the engine.
  2. Backflush the heater core. Refer to FLUSHING .
  3. Start the engine.
  4. Select the FLOOR mode.
  5. Select the minimum blower speed.
  6. Select the maximum temperature setting.
  7. Feel the temperature of the inlet and outlet hoses at the heater core.
Does the inlet hose feel warmer than the outlet hose?		 Go to Step 8  Go to Step 10 
8 Replace the heater core. Refer to Heater Core Replacement .
Is the repair complete?		 Go to Step 10  -
9 Repair the low engine temperature concern. Refer to ENGINE FAILS TO REACH NORMAL OPERATING TEMPERATURE in Engine Cooling.
Is the repair complete?		 Go to Step 10  -
10 Operate the system in order to verify the repair.
Does the system operate correctly?		 System OK Go to Step 2 
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