Freelander System Description and Operation
AIR CONDITIONING
DESCRIPTION AND OPERATION
82-21
Heater Distribution and Blend Unit Control
Blower unit air flow, having passed through the evaporator passes into the heater blend unit to be heated, if required.
It is then directed into the vehicle interior in accordance with the flap positions, which are designated by the air
distribution control on the fascia panel. A heater flap controls the amount of air flowing through the heater matrix, this
flap is moved in response to temperature selection using the knob on the control panel.
The distribution control moves the flaps which control the direction of the air flow into the interior of the vehicle.
Compressor and Cooling Fan Operating Conditions
The Engine Control Module (ECM) controls the compressor and cooling fan operation in response to signals received
from the refrigerant pressure sensor, evaporator temperature sensor and engine coolant temperature sensor, either
directly or on the CAN Bus from the instrument pack. The refrigerant pressure can be low, medium or high, the system
operating characteristics applicable for each condition is shown in the following table:
* With pressure below the low pressure limit, the cooling fans will always be off unless air conditioning is running whilst
evaporator temperature drops below minimum. If evaporator temperature drops below minimum, the cooling fans are
required to prevent cabin temperature cycling.
The engine management system also drives fan speed based on engine temperature. A faster cooling fan request
from either the engine cooling control or the A/C system will override another slow cooling fan speed request.
A/C Compressor On/
Off
Refrigerant Pressure Sensor
Operating Range
Action
Off
MED range
Air Con MED limit reached, cooling fans switched to High
speed.
Off
NORMAL range
Normal Condition, Low fan speed - no additional action
Off
HIGH range
COMPRESSOR NOT ALLOWED TO BE TURNED ON,
cooling fans at high speed
Off
LOW range
COMPRESSOR NOT ALLOWED TO BE TURNED ON*
On
MED range
Air Con MED limit reached, cooling fans to High speed
On
NORMAL range
Standard condition, low fan speed - no additional action
On
HIGH range
AIR CON COMPRESSOR MUST BE DISENGAGED
IMMEDIATELY, cooling fans set to High speed.
On
LOW range
AIR CON COMPRESSOR MUST BE DISENGAGED
IMMEDIATELY*
