Hummer H2. Manual - part 1967

16

2. Inspect the hose for debris by blowing shop air 

through one end of the hose while covering the 
other end with a shop towel.  

3. Observe the amount of debris collected in the shop 

towel.  

 
Did a large amount of debris collect in the shop towel?

Go to 

Step 18

Go to Step 19

17

1. Replace the expansion device. Refer to Expansion 

(Orifice) Tube Replacement .  

2. If the expansion device was restricted, observe the 

type of debris present.  

Are metal flakes present?

Go to 

Step 12

Go to Step 13

18

If a large amount of debris was collected in the shop towel 
from the compressor hose assembly, perform the 
following procedure: 

1. Replace the accumulator. Refer to Accumulator 

Replacement .  

2. Install an A/C refrigerant filter. Refer to Air 

Conditioning (A/C) Refrigerant Filter 
Installation .  

 
Is the repair complete?

Go to 

Step 19

-

19

Install the suction and the discharge lines. Refer to 
Suction Hose Replacement and to Discharge Hose 
Replacement . 
Are the repairs complete?

Go to 

Step 21

-

20

1. Install the suction and the discharge lines. Refer to 

Suction Hose Replacement and to Discharge 
Hose Replacement .  

2. Install an A/C refrigerant filter. Refer to Air 

Conditioning (A/C) Refrigerant Filter 
Installation .  

3. Recharge the A/C system. Refer to Refrigerant 

Recovery and Recharging .  

Are the repairs complete?

Go to 

Step 21

-

1. Record the low and the high side pressures and the 

panel outlet air temperature after you perform the 
repairs.  

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

HEATING PERFORMANCE DIAGNOSTIC 

Heating Performance Diagnostic 

21

2. Compare the pressures and the panel outlet 

temperature to those listed in the A/C Performance 
Chart. Refer to Air Conditioning (A/C) System 
Performance Test .  

Are the readings within the specified ranges as shown on 
the A/C Performance Chart?

Go to 

Step 22

Go to Air Conditioning 

(A/C) System Performance 

Test

22

Operate the system in order to verify the repair. 
Did you find and correct the condition?

System 

OK

Go to Symptoms - HVAC 

Systems - Automatic in 

HVAC Systems - Automatic

Step

Action

Yes

No

DEFINITION: Heating system performance.

1

Were you sent here from Symptoms or another diagnostic 
table?

Go to 

Step 2

Go to Too Cold in 

Vehicle in 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

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?

CAUTION:

Refer to Moving Parts and Hot Surfaces Caution in 
Cautions and Notices.

Go to 

Step 7

Go to Step 4

4

1. Install a thermometer into the center IP 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.  

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

DEFROSTING INSUFFICIENT 

6. Record the temperature at the following locations: 

z

The center IP PANEL air outlet  

z

The heater core outlet hose  

7. Compare the recorded temperatures.  

Are the two 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: 

z

The cowl  

z

The recirculation door  

z

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 - HVAC Systems - 
Automatic in HVAC Systems - Automatic.  

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 in Engine 
Cooling. 
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

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

Defrosting Insufficient 

Step

Action

Yes

No

DEFINITION: Time required to defrost the windshield is longer than normal.

1

Were you sent here from Symptoms or another 
diagnostic table?

Go to 

Step 2

Go to Symptoms - HVAC 

Systems - Automatic in HVAC 

Systems - Automatic

2

1. Start the engine.  

2. Select the DEFROST mode.  

3. Select the maximum blower speed.  

Does sufficient air flow from the defroster outlets?

Go to 

Step 3

Go to Step 10

3

Measure the engine operating temperature. 
Does engine reach a normal operating temperature?

Go to 

Step 10

Go to Step 8

4

1. Select the minimum blower speed.  

2. Select the warmest temperature setting. 

3. Feel the temperature of the inlet and outlet hoses 

at the heater core.  

Does the inlet heater hose feel warmer than the outlet 
heater hose?

CAUTION:

Refer to Moving Parts and Hot Surfaces 
Caution in Cautions and Notices.

Go to 

Step 11

Go to Step 5

5

Test the operation of the A/C compressor clutch. 
Does the A/C compressor clutch engage?

Go to 

Step 7

Go to Step 6

6

Repair the A/C compressor clutch. Refer to HVAC 
Compressor Clutch Does Not Engage in HVAC 
Systems - Automatic. 
Is the repair complete?

Go to 

Step 14

-

7

Perform the A/C system performance test. Refer to 
Air Conditioning (A/C) System Performance Test .
Is the A/C system operating within the specifications?

Go to 

Step 9

Go to Step 12

8

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 14

-

9

Inspect for correct operation of the recirculation door.
Is the recirculation door operating correctly?

Go to 

Step 14

Go to Step 13

10

Repair the air delivery concern. Refer to Air Delivery 
Improper in HVAC Systems - Automatic. 
Is the repair complete?

Go to 

Step 14

-

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2