L322 Range Rover System Description and Operation
AIR CONDITIONING
82-44
DESCRIPTION AND OPERATION
Recirculation Flaps
Unless the recirculation flaps are manually selected closed, using the recirculation switch on the control panel or the
steering wheel switch, they are normally open, but automatically closed by the ATC ECU under certain conditions.
Rapid Cooling: For rapid cooling of the passenger compartment, when the A/C system is selected on, if the driver's
side reference value is less than –20% and the ambient temperature is more than 6
°
C (43
°
F), the ATC ECU closes
the recirculation flaps. The ATC ECU opens the recirculation flaps after 12 minutes (temperate climates) or 20 minutes
(hot climates), if the driver's side reference value increases to more than –5% or if the ambient temperature decreases
to 6
°
C (43
°
F).
Pollution: When the ATC ECU detects a high level of pollutants, it sets the recirculation flaps to the recirculation
position for:
l
3 minutes if the A/C system is in the heating mode
l
10 minutes if the A/C system is in the cooling mode.
After the recirculation time period, the ATC ECU returns the recirculation flaps to the fresh air position. After 1 minute,
if the pollutants are still present, the ATC ECU repeats the recirculation cycle.
Ignition Off: If the recirculation flaps are in the recirculation position when the ignition is switched off, the ATC ECU
automatically sets them to the fresh air position, to ensure that fresh air is available if a fault occurs with the
recirculation flap drive circuit at the next ignition on. When the ignition is switched on, the ATC ECU sets the
recirculation flaps to the position they were in at ignition off.
Distribution Flaps
When a manual distribution selection is made on the control panel, the ATC ECU moves the distribution flaps to preset
positions. When the system is in the automatic mode, the ATC ECU uses maps of the driver's side reference value
to determine the position of the distribution flaps. Each distribution flap has a separate map, and there are separate
maps for temperate and hot climates. The mapped positions of the face level distribution flaps are given a correction
factor from the sunlight sensor inputs. The mapped positions of the distribution flaps are overridden by special
programmes, as follows:
Condensation Prevention: To prevent condensation on the windscreen, the ATC ECU closes the windscreen flaps for
12 seconds each time the engine starts. If a manual distribution selection is made during the 12 seconds, the
windscreen flaps revert to normal control.
The ATC ECU also closes the windscreen flaps when the reference value is less than 90% with the recirculation flaps
closed and the compressor is disengaged.
Cold Start: When the engine starts, if the system is in the automatic mode, the driver's side reference value is 100%
and the heater matrix temperatures is less than 30
°
C (86
°
F), the ATC ECU closes the face level and footwell flaps
and opens the windscreen flaps.
Duct Purging: After a cold start, if the system is in the automatic mode and the reference value is 100%, the ATC ECU
keeps the face level flaps closed until one of the heater matrix temperatures exceeds 60
°
C (140
°
F). The ATC ECU
then fully opens the face level flaps for 25 seconds to purge the ducts of cold air. After the purge the face level flaps
revert to normal automatic control. If, before or during the purge process, the reference value decreases below 100%,
the ignition has been on for 15 minutes, or a manual distribution selection is made, then the purge process is
cancelled.
Blower Control
In the automatic mode, blower speed is determined from reference temperature maps. In general terms, the more
heating or cooling required to achieve the temperature selected on the control panel with the driver's side temperature
switch, the faster the blower speed.
When maximum cooling is first required in the automatic mode, the ATC ECU runs the blower at full speed for a fixed
period regardless of any drop in passenger compartment temperature. Different time periods are incorporated for the
following markets:
l
NAS and Gulf States
l
Europe and ROW
l
Japan.
