Freelander System Description and Operation
AIR CONDITIONING
82-20
DESCRIPTION AND OPERATION
Operation
General
Air conditioning operates only while the engine is running and the blower in the heater assembly is on (any speed).
Fresh or recirculated air can be selected with or without the air conditioning being on, provided the ignition is on.
Air Conditioning
When the air conditioning switch is selected on, the indicator lamp in the switch illuminates and an air conditioning
request signal is input to the ECM via the instrument pack and CAN Bus.
On vehicles from 2003 model year, when the automatic on function is selected on, an air conditioning request signal
is input to the ECM via the instrument pack and the CAN bus.
The air conditioning request signal consists of a positive voltage supply via the blower switch and A/C switch, hard
wired to the instrument pack. The instrument pack interprets the A/C request signal and informs the ECM of the
condition using a message on the CAN Bus.
The signals from the refrigerant pressure sensor and the evaporator temperature sensor are supplied to the
instrument pack, which calculates the additional engine load and the cooling fan speed and transmits them to the
instrument pack on the CAN Bus.
On receipt of the air conditioning request signal, the ECM switches air conditioning on by signalling the compressor
clutch relay module to engage the compressor clutch and the cooling fan controller to run the cooling fans at the
appropriate speed using a PWM signal. The engine drives the compressor to circulate the refrigerant. The blower
draws fresh or recirculated air through the evaporator. As the air flows through the evaporator, moisture condenses
out from the relatively warm air onto the cold evaporator. The dehumidified air is then fed into the heater assembly,
from where it is distributed to the vehicle interior.
When the air conditioning switch is selected off, or if the blower is selected off, the indicator lamp in the air conditioning
switch extinguishes and the air conditioning request signal is removed from the ECM.
On vehicles from 2003 model year, when the automatic on function is selected off, or the blower is selected off, the
air conditioning signal is removed from the ECM.
The ECM then switches air conditioning off by signalling the relay module to disengage the compressor clutch and
cooling fan controller to terminate the operation of the cooling fans.
Blower Control
The blower can be operated at any one of four speeds by rotating the blower switch to the required position. When
the blower is switched off the air conditioning system will not operate.
The fresh air/recirculation flap has two positions and is operated by pressing the button in the centre console. In the
recirculation position, air is drawn into the heater from the vehicle by closing the exterior air inlet and opening the
interior inlet. In the fresh air position, air is drawn into the heater from outside the vehicle by opening the exterior air
inlet and closing the interior inlet.
