Hummer H2. Manual - part 1966

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

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

3

z

Restricted air flow  

z

Damaged condenser cooling fins  

z

Inspect for missing or misaligned air baffles.  

 
Do the following conditions exist?

Go to 

Step 4

Go to Step 6

4

Repair the air flow restriction. 
Is the repair complete?

Go to 

Step 9

-

5

Repair the cooling fan operation fault. Refer to Fan Clutch 
Diagnosis in Engine Cooling. 
Is the repair complete?

Go to 

Step 9

-

6

Feel the liquid line on both sides of the expansion device.Is 
the temperature the same before and after the expansion 
device?

CAUTION:

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

Go to 

Step 7

Go to Step 8

7

Replace the damaged/faulty orifice tube. Refer to 
Expansion (Orifice) Tube Replacement . 
Is the repair complete?

Go to 

Step 9

-

8

Air is in the refrigerant system, or the system is 
overcharged. Refer to the view screen on the J 43600 for 
foreign gas content in the refrigerant. See Special Tools 
and Equipment . 
Recover and recharge the A/C system. Refer to 
Refrigerant Recovery and Recharging . 
Is the repair complete?

Go to 

Step 9

-

9

1. Record the low and high side pressures and the 

instrument panel (I/P) outlet air temperature after 
repairs are performed.  

2. Compare the pressures and 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?

Go to 

Step 10

Go to Air Conditioning 

(A/C) System Performance 

Test

10

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

System 

OK

Symptoms - HVAC 

Systems - Automatic in 

HVAC Systems - Automatic

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

Step

Action

Yes

No

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

z

A restriction in the A/C system.  

z

Debris in the A/C system.  

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

Feel the liquid line before the expansion device.Is the 
liquid line cold before the expansion device?

CAUTION:

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

Go to 

Step 3

Go to Step 8

3

Feel along the surfaces of the following high side 
components: 

z

The compressor discharge hose  

z

The condenser  

z

The liquid line between the condenser and the 
expansion device  

 
Did you detect an abrupt drop in temperature along the 
surfaces of any of the listed components?

Go to 

Step 7

Go to Step 4

4

1. Feel the liquid line at the expansion device location 

for extreme cold, possibly accompanied by heavy 
frost.  

2. Feel along the liquid line beyond the expansion 

device location for warm temperature.  

Is the liquid line extremely cold at the expansion device 
location and warm beyond the expansion device location?

Go to 

Step 11

Go to Step 5

5

Feel along the surfaces of the following low side 
components: 

z

The evaporator inlet tube between the expansion 
device and the evaporator core  

z

The evaporator outlet tube between the evaporator 
core and the compressor  

z

The accumulator  

z

The compressor suction hose  

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

 
Did you feel an abrupt temperature change along the 
surfaces of any of the listed components?

Go to 

Step 7

Go to Step 6

6

Feel along the surfaces of the low and the high side 
components: 

z

The evaporator inlet tube between the expansion 
device and the evaporator core  

z

The evaporator outlet tube between the evaporator 
core and the accumulator  

z

The accumulator  

z

The compressor suction hose  

z

The compressor discharge hose  

z

The condenser  

z

The evaporator inlet tube between the condenser 
and the expansion device  

 
Are the temperatures of these components only mildly 
warm?

Go to 

Step 14

Go to Step 8

7

1. Recover the refrigerant. Refer to Refrigerant 

Recovery and Recharging .  

2. Remove the restriction from the component, or 

replace the component which produced an abrupt 
temperature drop.  

Is the repair complete?

Go to 

Step 9

-

8

1. Recover the refrigerant and evacuate the system. 

Refer to Refrigerant Recovery and Recharging .  

2. Record the weight of the recovered refrigerant.  

3. Compare the weight of the recovered refrigerant 

with the system capacity. Refer to Refrigerant 
System Capacities .  

Is the weight of the recovered refrigerant charge greater 
than 75% of the total system capacity?

Go to 

Step 9

Go to Step 10

9

Recharge the A/C system. Refer to Refrigerant 
Recovery and Recharging . 
Is the cooling performance improved?

Go to 

Step 21

Go to Step 10

10

1. Leak test the system. Refer to Leak Testing .  

2. Repair any leaks.  

Go to 

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

Is the repair complete?

Step 21

-

11

The expansion device is restricted. 
Replace the expansion device. Refer to Expansion 
(Orifice) Tube Replacement . 
Are metal flakes present?

Go to 

Step 12

Go to Step 13

12

1. Remove the suction line from the vehicle. Refer to 

Suction Hose Replacement .  

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 20

13

If the expansion device was restricted with a brown or 
black residue, perform the following procedure: 

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

2. Replace the accumulator. Refer to Accumulator 

Replacement .  

 
Are the repairs complete?

Go to 

Step 21

-

14

1. Recover the refrigerant. Refer to Refrigerant 

Recovery and Recharging .  

2. Disconnect the suction and the discharge lines from 

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

3. Inspect for the presence of debris in the compressor 

suction port.  

Is debris present in the compressor suction port?

Go to 

Step 15

Go to Step 19

15

1. Remove the debris from the suction port.  

2. Inspect the expansion device for damage or debris. 

Refer to Expansion (Orifice) Tube Replacement . 

Did you find evidence of damage or debris?

Go to 

Step 17

Go to Step 16

If the expansion device does not show any signs of 
damage or debris, perform the following procedure: 

1. Remove the suction line from the vehicle. Refer to 

Suction Hose Replacement .  

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2