Hummer H1 (2006+). Manual - part 322

11-22 Heating/Ventilation/Air Conditioning (HVAC)

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Removal

CAUTION: To avoid potential thread or fitting damage, hand start connections before using wrenches. 

1.

Discharge the air conditioning system.

2.

Disconnect the hose from the condenser and remove the O-ring. Discard the O-ring (Figure  11-11).

3.

Remove the hose and the O-ring from the receiver/dryer. Discard the O-ring.

Installation

1.

Lubricate the O-ring with PAG oil and secure the hose to the condenser with the nut torque to 12 lb-ft. (16 N·m). 

2.

Lubricate the O-ring with PAG oil, position on the hose, and secure the hose to the receiver/dryer. Using two wrenches for
equalized support, tighten to 11-13 lb-ft. (15-18 N•m).

3.

Evacuate and charge the air conditioning system.

4.

Check the system for leaks.

5.

Check the air conditioning system operation.

Receiver/Dryer-To-Evaporator Core Hose 

WARNING:  Air conditioning system components are subject to high pressure R-134a gas. Always discharge pres-
sure and contain refrigerant using approved service equipment. Use extreme care when handling R-134a. Direct
contact with skin may cause frostbite. Do not smoke in areas where R-134a is stored or used. Failure to follow these
warnings may result in serious injury.

Removal

1.

Discharge the air conditioning system.

2.

Disconnect the hose from the receiver/dryer and remove the O-ring. Discard the O-ring (Figure  11-11).

3.

Disconnect the auxiliary hose connection (if equipped).

4.

Remove the hose and the O-ring from the expansion valve manifold block. Discard the O-ring (Figures 11-9 and 11-11)

Installation

1.

Lubricate the two O-rings with PAG oil and position on the hose.

2.

Secure the hose to the expansion valve manifold block. Using two wrenches for equalized support, tighten to 11-13 lb-ft. (15-
18 N•m).

3.

Torque the auxiliary unit line to 11-13 lb-ft. (15-18 N•m).

4.

Secure the hose to the receiver/dryer. Using two wrenches for equalized support, tighten to 11-13 lb-ft. (15-18 N•m) (Figure
 11-12).

5.

Leak test the system.

CONDENSER REPLACEMENT

Removal

WARNING:  Air conditioning system components are subject to high pressure R-134a gas. Always discharge pres-
sure and contain refrigerant using approved service equipment. Use extreme care when handling R-134a. Direct
contact with skin may cause frostbite. Do not smoke in areas where R-134a is stored or used. Failure to follow these
warnings may result in serious injury.

1.

Discharge the air conditioning system.

NOTE: Cover all the open lines to prevent contamination.

2.

Disconnect the two pressure hoses from the condenser and remove the O-rings. Discard the O-rings.

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 Heating/Ventilation/Air Conditioning (HVAC)  11-23

Figure 11-11:   Condenser Replacement 

3.

Remove the two screws holding the fuel cooler to the condenser (Figure  11-11).

4.

Remove the four screws holding the A/C condenser to the trans oil cooler.

5.

Remove the condenser carefully from between the fuel cooler and the trans oil cooler.

Installation

1.

Secure the condenser to the trans oil cooler with the four screws (Figure  11-11).

2.

Secure the fuel cooler to the condenser with the two screws.

3.

Lubricate the two O-rings with PAG oil and install the pressure lines to the condenser torque to 12 lb-ft. (16 N·m).

4.

Evacuate and charge the air conditioning system.

RECEIVER/DRYER REPLACEMENT

Removal

FUEL COOLER

CONDENSER

CHARGED AIR

COOLER

RADIATOR

TRANS OIL 

COOLER

11-24 Heating/Ventilation/Air Conditioning (HVAC)

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WARNING:  Air conditioning system components are subject to high-pressure R-134a gas. Always discharge pres-
sure and contain refrigerant using approved service equipment. Use extreme care when handling R-134a. Direct
contact with skin may cause frostbite. Do not smoke in areas where R-134a is stored or used. Failure to follow these
warnings may result in serious injury.

NOTE: The receiver/dryer will quickly absorb water from the atmosphere when not sealed. Do not leave the system open during
service. The receiver/dryer should be replaced any time major components are replaced. If in doubt, replace the unit. 

1.

Discharge the air conditioning system.

2.

Disconnect the electrical connector from the low pressure switch (Figure  11-12).

NOTE: Cover all the open lines to prevent contamination.

3.

Disconnect the two hoses from the receiver/dryer and remove the O-rings. Discard the O-rings.

4.

Remove the two clamps and the receiver/dryer from the bracket.

Figure 11-12:   Receiver/Dryer

Installation

1.

Secure the receiver/dryer to the bracket with the two clamps. Position the hose attachment ports to the front and the rear of the
vehicle (Figure  11-12).

2.

Lubricate the two O-rings with PAG oil and position on the hose fittings.

3.

Connect the two hoses to the receiver/dryer.

4.

Connect the electrical connector to the low pressure switch.

5.

Test the system for leaks.

LOW PRESSURE CUTOFF SWITCH

The low pressure cutoff switch is mounted on the receiver/dryer. The switch is wired in series with the compressor activation cir-
cuit. Should pressure drop below the switch setting, the switch will open and interrupt current flow to the compressor clutch. The
switch will prevent damage to the system from lack of oil flow due to inadequate charge or very low ambient temperatures. The
switch will close when the system pressure rises to safe levels (Figure  11-16).

HOSE

HOSE

LOW 

BRACKET

RECEIVER

CLAMPS

PRESSURE SWITCH

DRYER

CONNECTOR

O-RINGS

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 Heating/Ventilation/Air Conditioning (HVAC)  11-25

LOW PRESSURE CUTOFF SWITCH REPLACEMENT

Removal

1.

Disconnect the pressure switch jumper connector from the receiver/dryer low pressure switch (Figure  11-13).

NOTE: The receiver/dryer is equipped with a schrader valve to prevent refrigerant loss with the pressure switch removed. Unscrew
the pressure switch as quickly as possible to avoid excessive loss of refrigerant.

2.

Using a wrench, remove the pressure switch from the receiver/dryer. 

Figure 11-13:   Low Pressure Cutoff Switch Mounting

Installation

1.

Thread the new pressure switch on the receiver/dryer fitting by hand and use a wrench to finish securing the pressure switch 
(Figure  11-13). 

NOTE: Install the pressure switch as quickly as possible to avoid excessive loss of refrigerant.

2.

Connect the pressure switch jumper electrical connector to the pressure switch.

3.

Check the pressure switch fitting for leaks using suitable leak-testing equipment.

HEATER HOSE REPLACEMENT

Engine coolant is routed through 5/8 inch diameter heater hose from the auxiliary coolant pump to the bottom fitting of the heater
shutoff valve. When the valve is open, coolant flows through another length of hose from the valve’s rearward lower fitting to the
front and rear heater core inlet ports, the heater core outlet hoses are routed to the rearward upper fitting on the heater shutoff valve.
The coolant return hose is routed from the forward upper heater shutoff valve fitting to the lower heater hose nipple (Figure
 11-15).

Removal

1.

Drain the cooling system (Refer to section 4).

2.

Move the constant tension clamps either end of the hose to be removed.

NOTE: Damage to the heater core can result if too much force is applied to the ports. If the hose is not easily removed by moderate
twisting and pulling, cut the hose just beyond the port. Then cut the hose remaining on the port lengthwise and remove it.

3.

Remove the hose ends from the fittings by twisting and pulling.

Installation

1.

With the clamps loosely in place, connect the hose ends to the respective fittings.

RECEIVER/

RECEIVER/DRYER

ELECTRICAL CONNECTOR

 DRYER

LOW PRESSURE

CUTOFF SWITCH