Air Conditioning
Air Conditioning
COMPONENT LOCATION 2.7L TdV6
COMPONENT LOCATION 3.0L TdV6
COMPONENT LOCATION 4.0L NA V6
COMPONENT LOCATION 5.0L NA V8
GENERAL
The A/C (air conditioning) system transfers heat from the vehicle interior to the outside atmosphere to provide the heater assembly with dehumidified cool air. The system consists of:
- A compressor.
- A condenser.
- A receiver drier.
- A thermostatic expansion valve.
- An evaporator.
- Low and high pressure refrigerant lines.
The system is a sealed, closed loop, filled with a charge weight of R134a refrigerant as the heat transfer medium. Oil is added to the refrigerant to lubricate the internal components of the compressor.
Operation of the air conditioning system is controlled by the ATC (automatic temperature control) module. The A/C (air conditioning) compressor circulates the refrigerant around the system by compressing low pressure, low temperature vapor from the evaporator and discharging the resultant high pressure, high temperature vapor to the condenser.
The A/C (air conditioning) compressor is a variable displacement unit which is driven by the engine accessory drive belt. On 2.7L/4.0L and 5.0L vehicles, the A/C (air conditioning) compressor is permanently driven directly from the pulley. On 3.0L diesel vehicles the A/C (air conditioning) compressor is driven via an electro-magnetic clutch.
To protect the refrigerant system from excessive pressure, a pressure relief valve is installed in the outlet side of the A/C (air conditioning) compressor. The pressure relief valve vents excess pressure into the engine compartment.
For additional information, refer to Control Components
A/C COMPRESSOR
2.7L TdV6
The A/C (air conditioning) compressor fitted to 2.7L TdV6 petrol vehicles is a variable displacement unit. The secondary accessory drive belt, driven by the engine crankshaft, drives the A/C (air conditioning) compressor via a pulley. Operation of the compressor is controlled by an electronic control valve working in conjunction with the ATC (automatic temperature control) module.
The A/C (air conditioning) compressor is a 7 cylinder swash plate unit with a minimum displacement of 1.6 cm3/rev (0.10 in3/rev) and maximum displacement of 171 cm3/rev (10.43 in3/rev). The ATC (automatic temperature control) module automatically adjusts the displacement of the A/C (air conditioning) compressor between the minimum and maximum values, to match the thermal load of the evaporator. By matching refrigerant flow and the thermal load of the evaporator, the ATC (automatic temperature control) module maintains cabin comfort whilst also considering fuel economy.
To protect the refrigerant system from unacceptably high pressure, a pressure relief valve is installed in the outlet side of the A/C (air conditioning) compressor. The pressure relief valve is set to open at 3.5 to 4.3 MPa (508 to 623 lbf/in2) and vents excess pressure into the engine compartment. The pressure relief valve closes again when the pressure decreases to 3.01 MPa (436 lbf/in2).
The pulley of the A/C (air conditioning) compressor incorporates a mechanical torque limiter, which disconnects the drive plate from the compressor shaft if torque increases to a level that indicates imminent compressor seizure.
3.0L TdV6
The A/C (air conditioning) compressor fitted to 3.0L TdV6 diesel vehicles is a variable displacement unit. The secondary accessory drive belt, driven by the engine crankshaft, drives the A/C (air conditioning) compressor via a pulley and an electromagnetic clutch. Operation of the clutch is controlled by a power feed from the ATC (automatic temperature control) module.
The A/C (air conditioning) compressor is a 7 cylinder swash plate unit with a minimum displacement of 1.6 cm3/rev (0.10 in3/rev) and maximum displacement of 163 cm3/rev (9.95 in3/rev). The ATC (automatic temperature control) module automatically adjusts the displacement of the A/C (air conditioning) compressor between the minimum and maximum values, to match the thermal load of the evaporator. By matching refrigerant flow and the thermal load of the evaporator, the ATC (automatic temperature control) module maintains cabin comfort whilst also considering fuel economy.
To protect the refrigerant system from unacceptably high pressure, a pressure relief valve is installed in the outlet side of the A/C (air conditioning) compressor. The pressure relief valve is set to open at 3.5 to 4.1 MPa (508 to 595 lbf/in2) and vents excess pressure into the engine compartment. The pressure relief valve closes again when the pressure decreases to 3.1 MPa (449 lbf/in2).
The clutch of the A/C (air conditioning) compressor incorporates a thermal cut-off fuse, which disconnects the power feed from the ATC (automatic temperature control) module if the temperature increases to 182 ± 5° C (360 ± 9° F).
4.0L NA V6
The A/C (air conditioning) compressor fitted to 4.0L NA V6 petrol vehicles is a variable displacement unit. The secondary accessory drive belt, driven by the engine crankshaft, drives the A/C (air conditioning) compressor via a pulley. Operation of the compressor is controlled by an electronic control valve working in conjunction with the ATC (automatic temperature control) module.
The A/C (air conditioning) compressor is a 7 cylinder swash plate unit with a minimum displacement of 1.6 cm3/rev (0.10 in3/rev) and maximum displacement of 171 cm3/rev (10.43 in3/rev). The ATC (automatic temperature control) module automatically adjusts the displacement of the A/C (air conditioning) compressor between the minimum and maximum values, to match the thermal load of the evaporator. By matching refrigerant flow and the thermal load of the evaporator, the ATC (automatic temperature control) module maintains cabin comfort whilst also considering fuel economy.
To protect the refrigerant system from unacceptably high pressure, a pressure relief valve is installed in the outlet side of the A/C (air conditioning) compressor. The pressure relief valve is set to open at 3.5 to 4.3 MPa (508 to 623lbf/in2) and vents excess pressure into the engine compartment. The pressure relief valve closes again when the pressure decreases to 3.01 MPa (437 lbf/in2).
The pulley of the A/C (air conditioning) compressor incorporates a mechanical torque limiter, which disconnects the drive plate from the compressor shaft if torque increases to a level that indicates imminent compressor seizure.
5.0L NA V8
The A/C (air conditioning) compressor fitted to 5.0L V8 petrol vehicles is a variable displacement unit. The secondary accessory drive belt, driven by the engine crankshaft, drives the A/C (air conditioning) compressor via a pulley. Operation of the compressor is controlled by an electronic control valve working in conjunction with the ATC (automatic temperature control) module.
The A/C (air conditioning) compressor is a 7 cylinder swash plate unit with a minimum displacement of 1.6 cm3/rev (0.10 in3/rev) and maximum displacement of 163 cm3/rev (9.95 in3/rev). The ATC (automatic temperature control) module automatically adjusts the displacement of the A/C (air conditioning) compressor between the minimum and maximum values, to match the thermal load of the evaporator. By matching refrigerant flow and the thermal load of the evaporator, the ATC (automatic temperature control) module maintains cabin comfort whilst also considering fuel economy.
To protect the refrigerant system from unacceptably high pressure, a pressure relief valve is installed in the outlet side of the A/C (air conditioning) compressor. The pressure relief valve is set to open at 3.5 to 4.1 MPa (508 to 595 lbf/in2) and vents excess pressure into the engine compartment. The pressure relief valve closes again when the pressure decreases to 3.1 MPa (449 lbf/in2).
The pulley of the A/C (air conditioning) compressor incorporates a mechanical torque limiter, which disconnects the drive plate from the compressor shaft if torque increases to a level that indicates imminent compressor seizure.
CONDENSER
NOTE:
5.0L NA V8 version shown other installations similar
The condenser transfers heat from the refrigerant to the surrounding air to convert the high pressure vapor from the compressor into a liquid. The condenser is installed immediately in front of the radiator. Two brackets on each end tank of the condenser attach the condenser to clips on the end tanks of the radiator.
The condenser is classified as a sub-cooling condenser and consists of a fin and tube heat exchanger core installed between two end tanks. Divisions in the end tanks separate the heat exchanger into a four pass upper (condenser) section and a two pass lower (sub-cooler) section. A connector block on the left end tank of the condenser provides connections for the high pressure lines from the A/C (air conditioning) compressor and the evaporator. Two pipes at the bottom of the right end tank of the condenser provide connections for the receiver drier.
RECEIVER DRIER
The receiver drier removes solid impurities and moisture from the refrigerant, and provides a reservoir for liquid refrigerant to accommodate changes of heat load at the evaporator.
The receiver drier is attached to the two stub pipes on the right end tank of the condenser. A collar, located on lands on the stub pipes and secured with a bolt, attaches the stub pipes to the receiver drier. A clamp secures the body of the receiver drier to a bracket welded to the right end tank of the condenser. The inlet and outlet ports of the receiver drier are the same size, so care must be taken to install the receiver drier the correct way round on the stub pipes; to assist with installation, the inlet port is identified with the word IN etched into the receiver drier.
Refrigerant entering the receiver drier passes through a filter and a desiccant pack, then collects in the base of the unit before flowing through the outlet stub pipe back to the condenser. The desiccant and the filter are non-serviceable; the complete unit must be replaced when a change of desiccant is required.
THERMOSTATIC EXPANSION VALVE
The thermostatic expansion valve meters the flow of refrigerant into the evaporator, to match the refrigerant flow with the heat load of the air passing through the evaporator.
The thermostatic expansion valve is a block type valve located behind the heater assembly, and attached to the inlet and outlet ports of the evaporator. The thermostatic expansion valve consists of an aluminum housing containing inlet and outlet passages. A ball and spring metering valve is installed in the inlet passage and a temperature sensor is installed in the outlet passage. The temperature sensor consists of a temperature sensitive tube connected to a diaphragm. The bottom end of the temperature sensitive tube acts on the ball of the metering valve. Pressure on top of the diaphragm is controlled by evaporator outlet temperature conducted through the temperature sensitive tube. The bottom of the diaphragm senses evaporator outlet pressure.
Liquid refrigerant flows through the metering valve into the evaporator. The restriction across the metering valve reduces the pressure and temperature of the refrigerant. The restriction also changes the liquid stream of refrigerant into a fine spray, to improve the evaporation process. As the refrigerant passes through the evaporator, it absorbs heat from the air flowing through the evaporator. The increase in temperature causes the refrigerant to vaporize and increase in pressure.
The temperature and pressure of the refrigerant leaving the evaporator act on the diaphragm and temperature sensitive tube, which regulate the metering valve opening and so control the volume of refrigerant flowing through the evaporator. The warmer the air flowing through the evaporator, the more heat available to evaporate refrigerant and thus the greater the volume of refrigerant allowed through the metering valve.
EVAPORATOR
The evaporator is installed in the heater assembly between the blower and the heater matrix, to absorb heat from the exterior or recirculated air. Low pressure, low temperature refrigerant changes from liquid to vapor in the evaporator, absorbing large quantities of heat as it changes state.
Most of the moisture in the air passing through the evaporator condenses into water, which drains out of the heater and through the floorpan, to the underside of the vehicle, through two drain tubes.
REFRIGERANT LINES
To maintain similar flow velocities around the system, the diameter of the refrigerant lines varies to suit the two pressure/temperature regimes. The larger diameters are installed in the low pressure/temperature regime and the smaller diameters are installed in the high pressure/temperature regime.
Low and high pressure charging connections are incorporated into the refrigerant lines for system servicing. Where auxiliary A/C (air conditioning) is installed, connections for the auxiliary refrigerant lines are incorporated near the engine bulkhead.
Under normal operating conditions, the smaller diameter pipes (A/C (air conditioning) compressor discharge, liquid refrigerant) are hot to the touch and the larger diameter pipes (A/C (air conditioning) compressor suction, gaseous refrigerant) are cold to the touch.
SYSTEM OPERATION
To accomplish the transfer of heat, the refrigerant is circulated around the system, where it passes through two pressure/temperature regimes. In each of the pressure/temperature regimes, the refrigerant changes state, during which process maximum heat absorption or release occurs. The low pressure/temperature regime is from the thermostatic expansion valve, through the evaporator to the compressor; the refrigerant decreases in pressure and temperature at the thermostatic expansion valve, then changes state from liquid to vapor in the evaporator, to absorb heat. The high pressure/temperature regime is from the compressor, through the condenser and receiver drier to the thermostatic expansion valve; the refrigerant increases in pressure and temperature as it passes through the compressor, then releases heat and changes state from vapor to liquid in the condenser.
A/C SYSTEM SCHEMATIC
NOTE:
A = Refrigerant liquid; B = Refrigerant vapor; C = Air flow
