Hummer H2. Manual - part 1965

AIR CONDITIONING (A/C) DIAGNOSTICS - PRESSURE ZONE B 

Air Conditioning (A/C) Diagnostics - Pressure Zone B 

12

1. Reinstall the accumulator. Refer to 

Accumulator Replacement .  

2. Flush the A/C system. Refer to Flushing .  

3. Add the specified amount of refrigerant oil to 

the accumulator. Refer to Refrigerant System 
Capacities .  

4. Recharge the A/C system. Refer to 

Refrigerant Recovery and Recharging .  

Are the repairs complete?

Go to Step 14

-

13

1. Add the specified amount of refrigerant oil to 

the accumulator. Refer to Refrigerant System 
Capacities .  

2. Install the accumulator. Refer to Accumulator 

Replacement .  

3. Recharge the A/C system. Refer to 

Refrigerant Recovery and Recharging .  

Are the repairs complete?

Go to Step 14

-

14

1. Record the low and high side pressures and the 

instrument panel (I/P) outlet air temperature.  

2. Compare the outlet temperatures to those listed 

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

Are the high and low side pressures and I/P panel 
outlet temperatures within specifications?

Go to Step 15

Go to Air 

Conditioning (A/C) 

System Performance 

Test

15

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: The low side pressure is higher than normal and the high side pressure is lower than 
normal. 

z

Malfunctioning A/C Compressor  

z

Refrigerant Under Charge  

Were you sent here from the A/C System Performance 

Go to Air Conditioning 

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

1

Test?

Go to 

Step 2

(A/C) System Performance 

Test

2

After continued operation of the air conditioning (A/C) 
system, do the low and the high side pressures equalize or 
become static?

Go to 

Step 5

Go to Step 3

3

Refer to the pressures recorded during the A/C System 
Performance Test. 
Inspect for the following conditions: 

z

The low side pressure is equal to or greater than the 
specified pressure range of the A/C Performance 
Table. Refer to Air Conditioning (A/C) System 
Performance Test .  

z

The high side pressure is less than the specified 
pressure range of the A/C Performance Table. Refer 
to Air Conditioning (A/C) System Performance 
Test .  

z

The low side refrigerant line at the compressor feels 
cool-to-warm.  

z

The high side refrigerant line at the compressor feels 
warm-to-hot.  

 
Do the listed conditions exist?

CAUTION:

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

Go to 

Step 5

Go to Step 4

4

Refer to the pressures recorded during the A/C System 
Performance Test. 
Inspect for the following conditions: 

z

The low side pressure is greater than the specified 
pressure range of the A/C Performance Table. Refer 
to Air Conditioning (A/C) System Performance 
Test .  

z

The high side pressure is less than the specified 
pressure range of the A/C Performance Table. Refer 
to Air Conditioning (A/C) System Performance 
Test .  

z

The low side refrigerant line at the compressor feels 

CAUTION:

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

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

warm.  

z

The high side refrigerant line at the compressor feels 
warm to hot.  

 
Do the listed conditions exist ?

Go to 

Step 5

Go to Air Conditioning 

(A/C) System Performance 

Test

5

The A/C system has a low refrigerant charge. 
Evacuate and recharge the A/C system. Refer to 
Refrigerant Recovery and Recharging . 
Is the procedure complete?

Go to 

Step 6

-

6

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

as the instrument panel (I/P) air outlet temperature 
after you perform the repairs.  

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 found on the 
A/C Performance Chart?

Go to 

Step 13

Go to Step 7

7

The A/C compressor is malfunctioning. 
Remove the expansion device and inspect for 
contamination. Refer to Expansion (Orifice) Tube 
Replacement . 
Did you find metal flakes on the expansion device?

Go to 

Step 9

Go to Step 8

8

Inspect the expansion device for a brown, powdery residue 
indicating desiccant in the A/C system. 
Is a brown, powdery residue present?

Go to 

Step 11

Go to Step 12

9

1. Remove the suction and the discharge lines from the 

compressor. Refer to Suction Hose Replacement 
and to Discharge Hose Replacement .  

2. Inspect for metal flake contamination at the line 

connections and the compressor ports.  

Is metal flake contamination present?

Go to 

Step 10

Go to Step 12

10

1. Replace the A/C compressor. Refer to Compressor 

Replacement .  

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

Conditioning (A/C) Refrigerant Filter 
Installation .  

3. Replace the orifice tube. Refer to Expansion 

(Orifice) Tube Replacement .  

4. Evacuate and recharge the A/C system. Refer to 

Refrigerant Recovery and Recharging .  

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

AIR CONDITIONING (A/C) DIAGNOSTICS - PRESSURE ZONE C 

Air Conditioning (A/C) Diagnostics - Pressure Zone C 

Is the repair complete?

Go to 

Step 13

-

11

1. Flush the A/C system. Refer to Flushing .  

2. Replace the orifice tube. Refer to Expansion 

(Orifice) Tube Replacement .  

3. Replace the A/C compressor. Refer to Compressor 

Replacement .  

4. Replace the accumulator. Refer to Accumulator 

Replacement .  

5. Evacuate and recharge the A/C system. Refer to 

Refrigerant Recovery and Recharging .  

Is the repair complete?

Go to 

Step 13

-

12

1. Replace the A/C compressor. Refer to Compressor 

Replacement .  

2. Evacuate and recharge the A/C system. Refer to 

Refrigerant Recovery and Recharging .  

Is the repair complete?

Go to 

Step 13

-

13

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: The low and the high side pressures are both higher than normal. 

z

Restricted condenser air flow  

z

Cooling fan malfunction  

z

Expansion device malfunction  

1

Were you sent here from the A/C System Performance 
Test?

Go to 

Step 2

Go to Air Conditioning 

(A/C) System Performance 

Test

2

1. With the engine idling, turn ON the A/C.  

2. Inspect for proper cooling fan operation. Refer to 

Cooling System Description and Operation in 
Engine Cooling.  

Are the cooling fans ON and operating properly?

Go to 

Step 3

Go to Step 5

Visually inspect for the following: 

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2