Hummer H1 (2006+). Manual - part 317

11-2 Heating/Ventilation/Air Conditioning (HVAC)

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System Description   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2
System Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-9
System Performance Checks   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2
Unit Service  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-32
Vacuum Door Motor  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-40
Vacuum Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-55
Water Control Valve  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-26
Water Control Valve Replacement   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-26

Pressure Hose Torque Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-18

HVAC SYSTEM DESCRIPTION

The heating, ventilating, and air conditioning system consists of the main unit, auxiliary unit, ducting for air, hoses to transport re-
frigerant, coolant hoses, a water valve, A/C compressor, condenser, receiver dryer, expansion valve, safety switches and vacuum
pump. Function of the system is controlled by the vehicle operator using the control panel on the console.

Auxiliary Unit

A secondary HVAC unit is used on all 4-passenger vehicles as standard equipment. The auxiliary unit includes a secondary heater
core, evaporator, expansion valve, blower motor and controls. Both the heater and A/C work in parallel with the main unit, requir-
ing that the main system be in operation to activate the auxiliary unit. The blower in the auxiliary unit is operated using a 3-position
switch on the console and provides 2 speeds and an off position.

A/C COMPRESSOR DESCRIPTION

All 2006 vehicles use a common Denso compressor. The compressor is belt driven off the engine accessory drive and utilizes an
electric clutch to engage and disengage the compressor drive. The compressor is lubricated with required GM PAG oil. The com-
pressor is specifically designed to operate with R134a refrigerant.

SYSTEM PERFORMANCE CHECKS

Before performing any air conditioning repair, perform the following:

Check the drive belt for wear, damage or loss of tension. Replace drive belt as necessary.

Check the compressor for secure mounting and proper alignment. Tighten loose hardware and align as necessary.

Visually inspect the compressor, hoses and other accessible parts of the system for damage or leaks. Look for patches of dirt,
dust, and oil build-up. Refrigerant leaks usually involve compressor oil loss. This is especially applicable to the clutch end of
the compressor.

Verify operation of the climate control system by performing the following:

With the mode (air flow) control knob set to OFF, run the engine to operating temperature (180°-240°F (82°-116°C)).

Rotate the temperature control knob clockwise until it stops at the warmest setting.

Rotate the mode control knob counterclockwise until it stops at the face setting.

Turn the fan control knob to any setting above LO and note the direction and temperature of the air flow.

Verify that heated air is coming from the instrument panel vents.

Rotate the mode control knob clockwise to the next setting, floor vents, and verify that heated air comes from the appro-
priate vents.

Continue checking the air flow positions, floor/defrost blend, and defrost.

NOTE: Any time the air flow control knob is placed in defrost or a defrost blend position (with an ambient temperature above
40°F), the compressor clutch engages to dehumidify the incoming air.

Rotate the temperature control knob counterclockwise to its coldest extreme. Verify that cold air comes from the defrost
vents. If the outside air temperature is 40°F or warmer, the refrigeration system will be responsible for cooling the air. If it
is cooler than 40°F, the compressor will not cycle and the incoming air will simply be the outside air directed into the
passenger compartment.

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Heating/Ventilation/Air Conditioning (HVAC) 11-3

Rotate the mode control knob counterclockwise until it stops at the Max A/C panel setting and verify that the compressor
clutch engages and the air becomes colder. Turn the mode dial to the A/C setting. Verify that the air recirculation door
closes and the system brings in outside air.

Check that the blower motor delivers air at four different speeds. If not, perform the electrical troubleshooting. Repair or
replace the blower motor, switch, relay or blower motor resistor card.

Check the water control valve operation, heater shutoff valve should open completely when the temperature control knob
is rotated clockwise.

Heating System Tests

In most cases, a low heat condition means an insufficient quantity of heated engine coolant is flowing through the heater core.
Check as follows:

Check the engine coolant level. If the level is low, add coolant and inspect for leaks. If the coolant level is correct, continue
with the tests.

Check the pressure cap on surge tank for improper sealing with tester J–24460-01 or equivalent. If the cap is OK, continue
with the tests. Replace the cap if it fails to seal and recheck the heater operation.

Set the heater controls to the highest heat setting.

Operate the engine until the coolant is at normal operating temperature (180-220° F or 82-113° C).

Check the temperature of the coolant flowing through the heater core inlet and outlet hoses.

• If both hoses feel hot and are about the same temperature, the water control valve is OK and the core is not restricted. Con-

tinue with the test.

• If both hoses are only warm (or even cool), the engine is either not at operating temperature, or a water pump or thermostat

problem has occurred.

• If the inlet hose is cool, or only slightly warm, a water control valve or vacuum solenoid problem has occurred. Test as de-

scribed in this section.

If heat output is still unsatisfactory but all else checks correctly, the problem is with the heat door in the main unit or in the
outlet ducts.

A/C System Leak Testing

There are two methods of detecting refrigerant leaks. One method is with the use of an electronic leak detector and the other uses a
fluorescent tracer dye in the refrigerant which is viewed at the leak site with an ultra violet (black) light.

Dye leak testing

R134a florescent dye will remain in the lubricant for the life of the vehicle as long as the vehicle’s AC system has not been flushed.
To perform a dye leak test, do the following:

Recover the existing R134a refrigerant and record the refrigerant weight.

Add R134a florescent dye J–41447 using the dye injector J–41459.

Recharge the AC system following the procedures outlined in chapter 11.

Check for leaks using the high intensity black light J-42220. If no leaks can be found, advise the customer of the dye in the
system and that it may need to be checked at a later date.

Electronic leak testing

Recommended electronic leak detector is the D-Tek, pocket portable model (Figure 11-1). It is self powered by NiCad batteries,
extremely compact, and will locate leaks as small as 1/4 ounce. The Kent-Moore Tool number is J–41995.

11-4 Heating/Ventilation/Air Conditioning (HVAC)

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Figure 11-1: D-Tek Leak Detector

The D-Tek probe is flexible and can be used to make a 360

check of each hose connector and fitting. The correct method of leak

testing fittings is shown in (Figure 11-2)

Figure 11-2: Leak Testing Technique at Connections

A/C system potential leak points are outlined in (Figure 11-3). Be sure to check each fitting and connector carefully with the D-
Tek tool.

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Heating/Ventilation/Air Conditioning (HVAC) 11-5

NOTE: Move the detector wand at a slow, consistent rate above and below and around fittings/connections. Carefully inspect all
hose connections to metal ferrules on crimp shells. Also test the small inspection holes on the shells.

Figure 11-3: A/C System Leak Check Points

CONNECTOR IDENTIFICATION

COMPRESSOR-OUT

MAIN EVAP - IN

CONDENSER - IN

MAIN EVAP - OUT

CONDENSER - OUT

L/P AUX TEE - IN

DRYER - IN

L/P AUX TEE - OUT

DRYER - OUT

L/P AUX TEE - OUT

H/P AUX TEE - IN

L/P AUX TEE - OUT

H/P AUX TEE - OUT

COMPRESSOR - FRONT SEAL

AUX EVAP - IN

SCHRADER VALVES

AUX EVAP - OUT

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