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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 92 (Heating, Ventilation, And Air Conditioning) >> Diagnostic Information and Procedures >> Heating Performance Diagnostic

Heating Performance Diagnostic

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. 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 Symptoms or another diagnostic table? Go to Step 2  Go to Symptoms - HVAC Systems - Manual
or
Symptoms - HVAC Systems - Automatic
2
  1. Start the engine.
  2. Allow the engine to idle.
Does the engine reach a normal operating temperature?		 Go to Step 3  Go to Step 9 
3
    CAUTION: Refer to Moving Parts and Hot Surfaces Caution .
  1. Allow the engine to idle.
  2. Select the FLOOR mode.
  3. Select the minimum blower speed.
  4. Select the warmest temperature setting.
  5. 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?		 Go to Step 7  Go to Step 4 
4
  1. Install a thermometer into the center I/P PANEL 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 warmest temperature setting.
  6. Record the temperature at the following locations:
    • The center I/P PANEL air outlet
    • The heater core outlet hose
  7. Compare the recorded temperatures.
Are the 2 temperature readings about equal?		 Go to Step 5  Go to Step 6 
5
  1. Inspect and repair the following areas of the vehicle for cold air leaks:
    • The cowl
    • The recirculation door
    • The HVAC module case
  2. Perform the necessary repairs.
Are the repairs complete?		 Go to Step 10  -
6
  1. Inspect the temperature door operation. Refer to Diagnostic System Check - Vehicle .
  2. Perform any necessary repairs.
Are the repairs complete?		 Go to Step 10  -
7
  1. Turn OFF the engine.
  2. Backflush the heater core.
  3. Start the engine.
  4. Select the FLOOR mode.
  5. Select the minimum blower speed.
  6. Select the warmest temperature setting.
  7. 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?		 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 .
Is the repair complete?		 Go to Step 10  -
10 Operate the system in order to verify the repair.
Did you find and correct the condition?		 System OK Go to Step 2 
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