Refrigerant System

AIR CONDITIONING

82-6

DESCRIPTION AND OPERATION

Description

General
Where fitted, the air conditioning system supplies cooled and dehumidified, fresh or recirculated air to the interior of 
the vehicle. Air is cooled by drawing it through the matrix of an evaporator. The air is then ducted into the heater 
assembly, from where it is distributed to the vehicle interior through the heating and ventilation system air ducts.

In the heater assembly, the temperature of the air distributed to the vehicle interior can be adjusted by passing a 
proportion, or all, of the cooled air through the heater matrix. The volume of air being distributed is controlled by the 
variable speed blower in the heater assembly. For details of temperature control and distribution. 
 

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 HEATING AND VENTILATION, DESCRIPTION AND OPERATION, Description.

The air conditioning system uses a pressure sensor and evaporator temperature sensor to provide operating condition 
feedback to the engine management system to enable the ECM to predict engine load and run the cooling fans in 
response to changing atmospheric conditions and driver demand.

Refrigerant System
The refrigerant system is a sealed closed loop system which is charged with Refrigerant R134a as the heat transfer 
medium. It works in combination with a blower unit, blend unit and control system to achieve the desired air 
temperature. ND-8 oil is added to the refrigerant to lubricate the internal components of the compressor. The 
refrigerant system comprises of the following main components connected together by refrigerant lines: 

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Compressor (variable load)

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Condenser (with modulator)

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Thermostatic expansion valve

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Evaporator

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 vapour in the evaporator, to absorb 
the heat. The high pressure/temperature regime is from the compressor, through the condenser and modulator 
(receiver/drier), back into the condenser where it is supercooled and then 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 vapour to liquid in the condenser.

Fan blown air is passed through the evaporator where it is cooled by absorption due to the low temperature refrigerant 
in the evaporator. Most of the moisture held in the air is condensed into water by the evaporator and drains away 
beneath the vehicle via a drain tube.

The compressor receives the returned low pressure, warm, vaporised refrigerant from the evaporator to complete the 
refrigeration cycle.