Hummer H1 (2006+). Manual - part 318

11-6 Heating/Ventilation/Air Conditioning (HVAC)

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A/C SYSTEM REFRIGERANT AND CAPACITY

The required refrigerant for HUMMER H1 A/C systems is R-134a. This is a colorless, odorless non-flammable, liquefied gas. Sys-
tem refrigerant capacity is: 2 lbs 4 oz.

A special refrigerant oil is required for use with R-134a which is polyalkaline glycol (PAG). This is the only oil that can be used
with R-134a refrigerant. More specifically, General Motors® PAG oil must be used with the A/C compressor on the HUMMER
H1.

CAUTION: R12 and R-134a refrigerants are not compatible. They must never be intermixed. Unsatisfactory cooling, rapid sludge
buildup, and compressor failure will result. 

CAPACITIES:

• Main unit with Aux 2 lbs 4oz

R-134a Refrigerant Precautions

To avoid product damage and personal injury, the following precautions should be followed when working with R-134a refriger-
ant.

• Wear safety goggles when servicing the A/C system as the refrigerant is under pressure.

• Never mix R-134a and R-12 refrigerants. They are incompatible and will cause severe damage to system components if 

mixed.

• Use an approved A/C service cart such as the Kent Moore J–39500-A to service the system. Recommended service carts are 

those capable of evacuation, recovery, recycling and recharging of systems with R-134a.

• The only compressor lubricant oil that can used with this system is General Motors PAG oil. Use of substitutes will result in 

compressor failure.

• Lubricate system fittings and o-rings with PAG oil for leak proof connections.

• Do not heat containers of R-134a above 125° F (52° C).

• Never puncture or incinerate containers of R-134a.

• Avoid breathing R-134a. The gas will irritate the nose, throat, and lungs. In addition, because R-134a is heavier than air, it

can displace oxygen in a confined and a poorly ventilated area. Be sure the work area is properly ventilated in case of acci-
dental release into the nearby atmosphere.

A/C System Pressure Test

System pressure testing involves measuring suction and discharge pressures with manifold gauge set J–39183-C or with the gauges
contained in A/C service cart J–39500-A. One gauge is for high side (discharge) pressures and one for low side (suction) pressures.
The gauges allow pressures to be checked while the system is in operation.

On models where access to the service ports is limited, coupler adapters J–39500-20A and J–39500-24A, will make gauge hose
connection easier.

Pressure Test Procedure

1.

Connect the gauge hoses on the service cart J–39500-A to the service ports on the suction and the discharge lines. The red hose
goes to the high side (discharge) port and the blue hose to the low side (suction) port.

2.

Note the pressure with the engine NOT running and the A/C system inoperative. There should be approximately 50 psi to 70
psi in the system. If pressure is lower or zero, a system leak exists. Add a small charge to the system. Then leak test and repair
as necessary before proceeding. 

3.

Start and run the engine at 1200 rpm.

4.

Set the A/C controls to the maximum cooling and set the blower to the highest speed.

5.

Verify that the compressor clutch engages. If the clutch fails to engage, diagnose and repair before proceeding.

6.

Record the low and the high side pressures. Depending on the engine speed and the shop ambient temperature, the low side
pressure will range from 36-55 psi (250-382 kPa) and the high side pressure from 164-238 psi (1130-1640 kPa). Ambient
temperatures will affect the refrigerant pressures in the system. On cool days, the pressures are lower, on hot days the
pressures are higher. Refer to system pressure comparison chart at the end of this section.

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NOTE: The relative humidity can effect outlet temperature, over 50% relative humidity will reduce outlet duct temperature.

7.

If the low and the high side pressures are OK, check the air temperature at the outlet duct closest to the evaporator with a
thermometer J–6742-03. The temperature should range from 59°F to 64°F with the inlet temperature between 76-85°F. Be
sure the thermometer tip is inserted into the duct to a depth of at least one inch (25 mm). 

8.

If the low and the high side pressures are incorrect and the air duct outlet temperatures are greater than the specified, refer to
the pressure test diagnosis charts for potential causes.

A/C Servicing Precautions

There are precautions that should be followed when servicing the A/C system. The precautions are necessary to avoid component
damage and personal injury.

• Wear eye protection when servicing the system. The refrigerant is under pressure and will cause injury if it contacts the 

eyes.

• Never perform system repairs until after the system has been fully discharged.

• Do not use refrigerant recovery, recycling, charging, and evacuation/discharge servicing equipment that does not meet SAE 

J–2210 standards.

• Never attempt to replace system components while the engine is running.

• Avoid having R-134a contact the skin. The refrigerant can cause an injury similar to frostbite. Exercise care when handling 

R-134a.

• Do not allow any type of open flame near R-134a.

• Avoid breathing R-134a fumes. The refrigerant will cause eye, nose, throat and lung irritation.

• Never mix R-12 and R-134a in the same system. The two refrigerants are not compatible. Mixing the two will result in fail-

ure of the compressor and other system components.

• Never use PAG oil from an unsealed container. The oil will quickly absorb moisture from the air if not sealed.

Recovering (Discharging) A/C System Refrigerant

1.

Shut the engine off.

2.

Connect the hoses from the service cart J–39500-A to the suction and the discharge service ports. The red hose goes to the
discharge side and the blue hose to the suction side. Use adapter fittings J–39500-20 and 24A if necessary. If the manifold
gauge set J–39183-C is being used, connect the center hose to a recovery tank or system.

NOTE: If both gauges indicate a zero reading, the system does not contain any refrigerant. Add a small charge, leak test and make
the necessary repairs before proceeding.

3.

Begin the recovery/discharge cycle as described in the service cart instructions.

4.

Recovery is complete when the service cart gauges read slightly below zero.

5.

Secure the service cart as described in the manufacturer’s instructions.

Recycling System Refrigerant

The J–39500-A service cart (from Kent Moore), will recycle R-134a refrigerant when necessary. The original recovered refrigerant
is moved through a combination filtration/dryer unit built into the cart. This unit removes impurities allowing refrigerant reuse.
Follow the manufacturer’s instructions carefully for the recycle process because incorrect use could result in moisture in the refrig-
erant. The recycle process is accomplished automatically when the service cart is in evacuation mode.

Evacuating the A/C System

CAUTION: Do not evacuate an A/C system that is not completely discharged. Check system pressures with a gauge set if unsure
about charge level.

The A/C system evacuation process involves applying 26-28 inches Hg to the A/C system for a minimum of 20 minutes. The ap-
plied vacuum removes moisture. A vacuum pump built into the service cart generates the necessary vacuum.

1.

Connect the service cart J–39500-A to the service ports.

11-8 Heating/Ventilation/Air Conditioning (HVAC)

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2.

Discharge the system.

3.

Connect the vacuum pump to the center hose on the manifold if the gauge set J–39183-C is being used.

4.

Turn the vacuum pump on and open the gauge valves.

NOTE: The high side gauge should drop to zero or below. If not, a blockage in the A/C system is indicated. Deduct 1 in. vacuum
from the maximum attainable reading for each 1000 ft. elevation above sea level.

5.

Evacuate the unit until the low pressure gauge reads 26-28 in. Hg.

6.

Turn the vacuum pump off and allow the system to sit undisturbed for 15 min to check for vacuum leaks. If the pressure rises,
diagnose the system leak.

7.

Continue the evacuation for thirty minutes after the correct gauge reading of 26-28 in. Hg vacuum has been achieved.

8.

Turn the gauge valves to the closed position after evacuation is complete.

9.

Turn off the vacuum pump and disconnect the center hose from the vacuum pump.

Checking/Adding Refrigerant Oil

It is not necessary to check or add oil as routine maintenance. It is necessary to add oil when the evaporator, condenser, compressor
or receiver/dryer has been replaced or there was a large leak. When a system is discharged, it is also necessary to replace any oil
carried out with the refrigerant.

CAUTION: All replacement compressors are shipped with 8 oz. (237 ml) of oil in the crankcase. This oil must be drained com-
pletely and replaced in like amount to the failed compressor. Add 2 oz. above what is found in the failed compressor. Failure to do
so will cause an overcharge of oil in the system and will lower cooling efficiency. An extreme overcharge condition may cause
early compressor failure.

1.

If a major component was replaced, add clean GM PAG oil as follows.

a.

Condenser – 1 oz. (30 ml).

b.

Evaporator – 3 oz. (84 ml).

c.

Receiver/Dryer – 2 oz. (60 ml).

d.

Auxiliary Unit - 2 oz. (60 ml).

e.

Compressor – see step 3.

f.

Any other known quantity of oil.

2.

Add oil to the system. Add directly into the component. Oil can also be added directly from the service cart after the system
evacuation.

3.

Check the oil in the compressor:

a.

Recover/discharge A/C system refrigerant.

b.

Remove the compressor.

c.

Tip the compressor on the hose connection end and drain into a clean container. Allow it to drain for ten minutes. Measure
and discard the oil.

d.

When the new compressor is received, drain the oil that was shipped inside. Replace the oil in an equal amount to that
which was drained from the old compressor. If less than one ounce (30 ml) is drained from the old compressor, add two
ounces (60 ml) to the new compressor. If more than one ounce (30 ml) is drained, replace the same amount in the new
one.

e.

Plug or block the ports and turn compressor over slowly several times.

4.

Perform the evacuation, recharging and the leak testing of system.

Charging The A/C System

NOTE: If the A/C system requires replacement of a major component, refrigerant oil must be added to the system to compensate
for the loss.

1.

Evacuate the A/C system. Follow the manufacturer’s recommended service procedures for the equipment being used.

2.

Connect the refrigerant source to the center hose if the manifold gauge set J–39183-C is being used.

3.

Open the refrigerant R-134a source to allow the refrigerant to flow into the system.

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4.

Purge the center hose, low-pressure hose and the high-pressure hose as follows:

a.

Slightly loosen the center hose at the manifold gauge set the center port until the refrigerant escapes, then tighten the hose.

b.

Open the high-pressure and the low-pressure gauge valves to allow refrigerant to flow into the high-pressure and the low-
pressure hoses.

c.

Turn the high-pressure and the low-pressure gauge valves clockwise to the OFF position.

d.

Purge the high-pressure and the low-pressure hoses at the service ports of the compressor.

WARNING:  Make sure high-pressure gauge valve is in closed position on manifold gauge set during charging.
Failure to do so will cause compressor to build pressure in refrigerant container. This could result in injury to per-
sonnel or damage to equipment if the container cracks.

5.

Start the engine and set the engine speed at 1500 rpm.

6.

Turn the A/C system to max cold and the blower fan on high speed.

NOTE: Keep the refrigerant container upright at all times so the refrigerant enters the system as a gas.

7.

Open the low-pressure gauge valve until the system is fully charged.

8.

Close the low-pressure gauge valve.

9.

Return the engine to normal idle.

10. Check the A/C system performance.

11. Disconnect and remove the service cart.

SYSTEM DIAGNOSIS

System diagnosis should begin with the system performance checks described in this section. The checks will help verify that a
problem actually exists as opposed to an incorrect setting by the vehicle operator.

In addition to the performance checks, problem verification will also involve pressure testing, leak testing, individual component
testing, air flow and temperature testing and refrigerant recovery, evacuation or recharge. The tools and equipment required for this
purpose are described in each procedure.

The diagnosis charts outline common heater and A/C problems. The potential causes are listed in order of probability (most-to-
least probable). However, the charts are guides only and will not outline all of the possible system faults that might occur. System
testing is still required for verification.

The primary diagnostic method of checking A/C system performance is the pressure test. The test is performed with manifold
gauge set J–39183-C. The gauges allow suction and discharge pressures to be checked while the system is operating. The pressure
test diagnosis charts describe common faults that cause incorrect system pressures.