Hummer H2. Manual - part 1964

Fig. 1: A/C System Pressure - Zone Classification 
Courtesy of GENERAL MOTORS CORP. 

A/C Performance Table 

Ambient Air 

Temperature

Relative 

Humidity

Service Port Pressure

Maximum Left Center 

Discharge Air Temperature

Low Side

High Side

13-16° C (55-65° F)

0-100%

200-283 kPa 

(29-41 psi)

945-1234 kPa 

(137-179 psi)

11° C (52° F)

19-24° C (66-75° F)

Below 40%

228-310 kPa 

(33-45 psi)

1082-1413 kPa 

(157-205 psi)

14° C (57° F)

Above 40%

248-338 kPa 

(36-49 psi)

1131-1469 kPa 

(164-213 psi)

15° C (59° F)

25-29° C (76-85° F)

Below 35%

276-379 kPa 

(40-55 psi)

1303-1696 kPa 

(189-246 psi)

18° C (64° F)

35-60%

276-379 kPa 

(40-55 psi)

1310-1709 kPa 

(190-248 psi)

18° C (64° F)

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

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

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

Above 60%

290-400 kPa 

(42-58 psi)

1358-1765 kPa 

(197-256 psi)

19° C (66° F)

30-35° C (86-95° F)

Below 30%

317-434 kPa 

(46-63 psi)

1544-2006 kPa 

(224-291 psi)

22° C (72° F)

30-50%

324-441 kPa 

(47-64 psi)

1558-2034 kPa 

(226-295 psi)

22° C (72° F)

Above 50%

365-510 kPa 

(53-74 psi)

1675-2179 kPa 

(243-316 psi)

26° C (79° F)

36-41° C (96-105° 

F)

Below 20%

400-552 kPa 

(58-80 psi)

1917-2503 kPa 

(278-363 psi)

28° C (82° F)

20-40%

393-546 kPa 

(57-79 psi)

1910-2496 kPa 

(274-357 psi)

28° C (82° F)

Above 40%

400-552 kPa 

(58-80 psi)

1910-2496 kPa 

(277-362 psi)

28° C (82° F)

42-46° C (106-115° 

F)

Below 20%

448-621 kPa 

(65-90 psi)

2172-2834 kPa 

(315-411 psi)

31° C (88° F)

Above 20%

462-634 kPa 

(67-92 psi)

2220-2896 kPa 

(322-420 psi)

32° C (90° F)

47-49° C (116-120° 

F)

Below 30%

531-731 kPa 

(77-106 psi)

2379-3116 kPa 

(347-452 psi)

43° C (109° F)

Step

Action

Yes

No

DEFINITION: The high and low side pressures may be normal or slightly less than normal. 

z

Air delivery concern  

z

Slight refrigerant under charge  

z

Refrigerant contamination  

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

Refer to the panel air outlet temperatures recorded 
during the A/C system performance test. 
Does the discharge air temperature between the right 
and left center panel outlets vary by more than 1-2° C 
(2-3° F)?

Go to Step 7

Go to Step 3

3

Did the customer mention that the A/C system output 
temperatures are good at first, but then turn warm 
during extended drives?

Go to Step 4

Go to Step 5

Increase engine speed to 2,000 RPM. 
During extended operation of the A/C system, does 

Go to Air 

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

4

the low side pressure decrease, possibly accompanied 
by heavy frost on the liquid line between the 
expansion device and the evaporator?

Conditioning (A/C) 

Diagnostics - 

Pressure Zone D

Go to Step 5

5

Refer to the pressures recorded during the A/C 
system performance test. 
Inspect for the following conditions: 

z

The high side pressure is slightly greater than 
the specified pressure ranges but still within 
Zone A on the A/C Pressure-Zone 
Classification Chart in the A/C System 
Performance Test. Refer to Air Conditioning 
(A/C) System Performance Test .  

z

The discharge line is hot.  

z

The suction line is cool.  

 
Do the listed conditions exist?

CAUTION:

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

Go to Step 7

Go to Step 6

6

Refer to the pressures recorded during the A/C 
system performance test. 
Inspect for the following conditions: 

z

The low side pressure is slightly lower than the 
specified pressure ranges but still within Zone 
A on the A/C Pressure-Zone Classification 
Chart in the A/C System Performance Test. 
Refer to Air Conditioning (A/C) System 
Performance Test .  

z

The discharge line is warm-to-hot.  

z

The suction line is cool-to-warm.  

 
Do the listed conditions exist?

CAUTION:

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

or 

Go to Step 8

Go to Too Hot in 

Vehicle in HVAC 

Systems - Automatic

The A/C system may be undercharged. 

1. Leak test A/C system. Refer to Leak Testing . 

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2

  

7

2. Recharge the A/C system to specifications. 

Refer to Refrigerant Recovery and 
Recharging .  

 
Is the repair complete?

Go to Step 14

-

8

The A/C system may be contaminated. 
View the J 43600 information screen for detection of 
foreign gases in the A/C system. See Special Tools 
and Equipment . 
Do foreign gases exist?

Go to Step 9

Go to Step 10

9

1. Evacuate the A/C system to a scavenging tank. 

Refer to Refrigerant Recovery and 
Recharging .  

2. Recharge the A/C system to specifications.  

Is the repair complete?

Go to Step 14

-

10

The A/C system may contain too much moisture or 
air. 

1. Evacuate and recharge the A/C system to 

specifications. Refer to Refrigerant Recovery 
and Recharging .  

2. Operate the A/C system and inspect the panel 

outlet air temperatures. Refer to Air 
Conditioning (A/C) System Performance 
Test .  

 
Are the panel outlet temperatures within the specified 
ranges of the A/C Performance Test Table?

Go to Step 15

Go to Step 11

11

The A/C system may contain too much refrigerant 
oil. 

1. Recover the refrigerant from the A/C system. 

Refer to Refrigerant Recovery and 
Recharging .  

2. Remove the accumulator. Refer to 

Accumulator Replacement .  

3. Drain and measure the refrigerant oil from the 

accumulator.  

 
Were more than 148 ml (5 oz) of refrigerant oil 
drained from the accumulator?

Go to Step 12

Go to Step 13

 

2004 Hummer H2 

2004 HVAC Heating, Ventilation and Air Conditioning - Hummer H2