Freelander System Description and Operation
AIR CONDITIONING
DESCRIPTION AND OPERATION
82-17
If the temperature at the evaporator falls low enough for ice to form on the fins, the ECM withholds or discontinues
engagement of the compressor clutch. When the temperature at the evaporator rises sufficiently, the ECM engages
the compressor clutch.
The evaporator temperature sensor is also used in conjunction with the refrigerant pressure sensor to facilitate
compressor load prediction for optimum idle speed control and load management. The A/C system places an extra
load on the engine when the compressor is operating, so the ECM automatically adjusts the idle speed to compensate
for the additional load.
ENGINE MANAGEMENT SYSTEM - SIEMENS, DESCRIPTION AND OPERATION, Description.
Refrigerant Pressure Sensor
The refrigerant pressure sensor is located in the refrigerant lines. On LHD vehicles with KV6 engines it is located at
the RH side of the engine compartment close to the outlet from the condenser in the refrigerant line leading to the
thermostatic expansion valve. On all other engine/vehicle derivatives the sensor is located in the same refrigerant line
at the LH side of the engine compartment. The refrigerant pressure sensor provides the ECM with a pressure input
from the high pressure side of the refrigerant system.
The ECM uses the signal from the refrigerant pressure sensor to protect the system from extremes of pressure, by
disengaging the compressor clutch. The signal is also used for cooling fan control. The temperature sensor used has
a low pressure range of 0 – 600 psi and provides the following functions:
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Provide a safety cut-out function if the refrigerant pressure goes either too high or too low.
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Indicate when the refrigerant pressure reaches such a point that additional cooling is required – if the pressure
reaches the medium point, the cooling fans will be switched to high speed.
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The pressure sensor is used in conjunction with the evaporator temperature sensor to predict compressor load
for load management at idle/part throttle.
The refrigerant pressure sensor is connected to the instrument pack, and the signal is relayed to the ECM from the
instrument pack via the CAN Bus.
Because the compressor is lubricated by oil suspended in the refrigerant, a low pressure signal from the sensor is
used by the ECM to prevent operation of the compressor unless there is a minimum refrigerant pressure, and thus
refrigerant and oil in the system.
Control Switches
The control switches consist of two latching push switches installed in the centre console, an air conditioning switch
and a fresh/recirculated air switch. Each switch contains an amber indicator lamp which illuminates when air
conditioning or recirculated air is selected, as applicable.
The A/C switch is supplied with a positive feed through the blower motor switch when one of the four blower speeds
is selected. When the A/C switch is selected, a signal is supplied to the instrument pack through a hard wire
connection. The instrument pack interprets the A/C request signal and transfers the request to the ECM via the CAN
bus.
INSTRUMENTS, DESCRIPTION AND OPERATION, Description.
On vehicles from 2003 model year, an automatic A/C on feature is introduced. This feature automatically selects A/C
on when the air distribution control is moved to the feet/screen or screen positions. A microswitch, which is operated
by the distribution control knob, is wired in parallel with the A/C switch and has the same functionality. The automatic
on function cannot be overridden and there is no indicator lamp to display when the A/C is active. The blower motor
switch must be in positions 1 to 4 before the automatic on function will operate.