Land Rover Body And Paint Air Bag And Safety Belt Rover Manual

							the ATCM also automatically sets the air source to
recirculated air, blower speed to maximum and
distribution to face. When maximum hot is selected,
the ATCM also automatically sets the air source to
fresh air, blower speed to maximum and distribution
to footwell.
•LH and RH Seat Heater Switches: Activates the
heater elements in the seat cushion and seat back at
one of two heat levels. The first press of the switch
energizes the heater elements at the higher heat
setting and illuminates two LED in the switch. A
second press of the switch sets the heater elements
to the lower heat setting and extinguishes one of the
LEDs. A further press of the switch de-energizes
the heater elements and extinguishes the second
LED. The seat heaters remain on until selected off
or the ignition is switched off.
•Blower Switch: For manual adjustment of blower
speed. The switch can rotate through 240°, from off
to maximum speed. Eight primary detents define the
off position and seven blower speeds. Minor detents
define small steps between the primary detents.
When blower speed is manually adjusted, amber
LEDs in the switch surround illuminate to indicate
the selected blower speed. The LEDs remain off
when blower speed is under automatic control.
•Automatic Mode Switch: Activates the automatic
modes for the A/C system, blower speed and
distribution. Separate amber LEDs in the automatic
mode switch illuminate to show when the blower
and the distribution are in automatic mode. Manually
selecting the blower speed or a distribution switch
extinguishes the related LED.
•Programmed Defrost Switch: Activates a program
that automatically selects: inlet air to fresh air;
distribution to screen only; blower to speed 5; rear
screen heater on; windshield heater on (where fitted),
A/C system to automatic mode. An amber LED in
the switch is illuminated while the defrost program
is active.
•Windshield Heater Switch: Energizes the
windshield heater for a set time period, until the
switch is pressed again or until the engine stops,
whichever occurs first. An amber LED in the switch
is illuminated while the heater is on.
•Rear Window Heater Switch: Enabled only with
the engine running. Pressing the switch energizes
the rear window heater for a set time period, until
the switch is pressed again or until the engine stops,
whichever occurs first. An amber LED in the switch
is illuminated while the heater is on.
•Auxiliary Climate Control Switch: Cycles the
auxiliary climate control system through the three
operating states of manual mode, automatic mode
and off. Two amber LEDs in the switch illuminate
to indicate the operating state: one LED is
illuminated for manual mode and two are illuminated
for automatic mode.
•Off Switch:Switches off all of the functions
controlled by the ATCM (all tell-tale LEDs are
extinguished). The temperature blend door is set to
the full cold position (if the A/C system is in the
automatic mode, if the A/C system is in the economy
mode the current door position is retained); the air
source is set to recirculation; the current distribution
settings are retained; the blower speed is set to zero.
Where fitted, the seat heater switches and the
auxiliary climate control switch can still be operated
without re-activating the ATCM. The ATCM is
re-activated, with all functions in the previous
operating state, by a second press of the off switch
or by pressing the economy switch. The ATCM can
also be re-activated, with the associated effect, by
the following switches:
•The automatic mode switch.
•Any air distribution switch.
•The blower switch.
•The programmed defrost switch.
•The recirculation switch.
(G421238) Technical Training42
Lesson 2 – ElectricalControl Components 
						

							•Economy Switch: Reduces the A/C compressor
output to a minimum displacement condition x 5%,
reducing the engine load required to operate the A/C
compressor. An amber LED in the switch is
illuminated when the economy mode is selected on.
•Recirculation Switch: For selection of fresh or
recirculated air. On models without pollution sensing,
an amber LED in the switch is illuminated when
recirculated air is selected. On models with pollution
sensing, the recirculation switch incorporates two
amber LED. The first press of the switch sets the
recirculation flaps to automatic mode and illuminates
one LED. A second press of the switch manually
selects recirculated air and illuminates the second
LED. A further press of the switch manually selects
fresh air and extinguishes the two LED.
•Distribution Switches (Windshield, Face and
Footwell): For manual selection of air distribution
in any combination of windshield, face and footwell
outlets. Each switch has a LED which illuminates
when the related distribution mode is selected.
•
Inputs and Outputs
Four electrical connectors provide the interface between
the ATCM and the vehicle wiring.
The control system sensors provide hardwired inputs to
the ATCM. The ATCM also uses the LIN bus to
communicate with the auxiliary climate control system
and the door motors in the heater assembly, and the
medium speed CAN bus to communicate with other
control modules on the vehicle.
ATCM Harness Connectors
NOTE: A = C1629; B = C1630; C = C2655; D = C2295
Control ComponentsLesson 2 – Electrical
43Technical Training (G421238) 
						

							ATCM Harness Connector C1629 Pin Details
Input/OutputSystemDescriptionPin No.
AutomaticManual
OutputYesYesSensor 5V reference voltage (refri-
gerant pressure, humidity, sunlight as
applicable)
1
InputYesNoPollution sensor NOx signal2
Input/OutputYesNoIn-vehicle temperature sensor signal3
InputYesYesRefrigerant pressure sensor signal4
InputYesNoSunlight sensor RH signal5
OutputYesNoPollution sensor PWM signal6
OutputYesYesBlower relay coil7
---Not used8
Input/OutputYesYesMedium speed CAN bus low9
Input/OutputYesYesMedium speed CAN bus high10
OutputYesNoPollution sensor power feed11
---Not used12
InputYesYesSensor ground (refrigerant pressure,
ambient air temperature, pollution,
humidity, in-vehicle temperature and
front seat temperature, as applicable)
13
InputYesNoPollution sensor HC/CO signal14
InputYesYesAmbient air temperature sensor signal15
InputYesNoHumidity sensor signal16
InputYesNoSunlight sensor LH signal17
InputYesYesWindshield heater relay18
InputYesYesWasher jets/exterior mirrors heater
relay
19
Input/OutputYesYesLIN bus (on models with auxiliary
climate control)
20
Input/OutputYesYesMedium speed CAN bus low21
(G421238) Technical Training44
Lesson 2 – ElectricalControl Components 
						

							Input/OutputSystemDescriptionPin No.
AutomaticManual
Input/OutputYesYesMedium speed CAN bus high22
InputYesYesCompressor solenoid valve -23
OutputYesYesCompressor solenoid valve +24
ATCM Harness Connector C1630 Pin Details
Input/OutputSystemDescriptionPin No.
AutomaticManual
---Not used1 and 2
Input/OutputYesYesRecirculation motor power feed/
ground
3
Input/OutputYesYesRecirculation motor power feed/
ground
4
---Not used5 to 8
InputYesYesRecirculation door motor feedback
potentiometer signal
9
---Not used10
InputYesYesDistribution and temperature blend
motor ground
11
OutputYesYesSensor power feed (evaporator
temperature, recirculation motor
feedback, as applicable)
12
OutputYesYesDistribution and temperature blend
motor power
13
Input/OutputYesYesDistribution and temperature blend
motor LIN bus
14
---Not used15 and 16
OutputYesYesBlower module power drive17
InputYesYesBlower motor voltage sense18
---Not used19
Control ComponentsLesson 2 – Electrical
45Technical Training (G421238) 
						

							Input/OutputSystemDescriptionPin No.
AutomaticManual
InputYesYesEvaporator temperature sensor signal20
---Not used21 to 23
InputYesYesRecirculation door motor ground24
ATCM Harness Connector C2295 Pin Details
Input/OutputSystemDescriptionPin No.
AutomaticManual
InputYesYesSeat heater power supply, right1
InputYesYesSeat heater power supply, left2
OutputYesYesPower supply to right front seat
heaters
3
InputYesYesRight front seat temperature sensor4
InputYesYesLeft front seat temperature sensor5
OutputYesYesPower supply to right front seat
heaters
6
ATCM Harness Connector C2655 Pin Details
Input/OutputSystemDescriptionPin No.
AutomaticManual
InputYesYesPermanent battery power supply1
---Not used2
OutputYesYesGround3
(G421238) Technical Training46
Lesson 2 – ElectricalControl Components 
						

							AMBIENT AIR TEMPERATURE
SENSOR
The ambient temperature sensor is a Negative
Temperature Coefficient (NTC) thermistor that provides
the ATCM with an input of external air temperature.
The sensor is attached to a bracket on the rear of the
bumper beam, on the vehicle center-line.
REFRIGERANT PRESSURE SENSOR
The refrigerant pressure sensor provides the ATCM
with a pressure input from the high pressure side of the
refrigerant system. The refrigerant pressure sensor is
located in the refrigerant line between the condenser
and the thermostatic expansion valve.
The ATCM supplies a 5 V reference voltage to the
refrigerant pressure sensor and receives a return signal
voltage, between 0 and 5 V, related to system pressure.
The ATCM uses the signal from the refrigerant pressure
sensor to protect the refrigerant system from extremes
of pressure and to calculate A/C compressor load on the
engine. The ATCM also transmits the A/C compressor
load value to the Engine Control Module (ECM), via
the medium speed CAN bus, instrument pack and high
speed CAN bus, for use in controlling the speed of the
engine cooling fan.
To protect the system from extremes of pressure, the
ATCM sets the A/C compressor to the minimum flow
position if the pressure:
•Decreases to 1.9 ± 0.2 bar (27.5 ± 3 lbf/in2): the
ATCM loads the A/C compressor again when the
pressure increases to 2.8 ± 0.2 bar (40.5 ± 3 lbf/in2).
•Increases to 33 ± 1 bar (479 ± 14.5 lbf/in2): the
ATCM loads the A/C compressor again when the
pressure decreases to 23.5 ± 1 bar (341 ± 14.5
lbf/in2).
EVAPORATOR TEMPERATURE
SENSOR
The evaporator temperature sensor is a NTC thermistor
that provides the ATCM with a temperature signal from
the downstream side of the evaporator. The evaporator
temperature sensor is installed in the right side of the
heater assembly casing.
Control ComponentsLesson 2 – Electrical
47Technical Training (G421238) 
						

							The ATCM uses the input from the evaporator
temperature sensor to control the load of the A/C
compressor and thus the operating temperature of the
evaporator.
IN-VEHICLE TEMPERATURE
SENSOR
The in-vehicle temperature sensor is a NTC thermistor
installed behind a grill on the driver side of the center
console finisher. The sensor is connected to a tube, the
other end of which is connected to a venturi on the side
casing of the heater. An air bleed from the heater,
through the venturi, induces a flow of air down the tube,
which draws cabin air through the grill and over the
sensor.
HUMIDITY SENSOR (WHERE
FITTED)
The humidity sensor is a capacitive device integrated
into the in-vehicle temperature sensor (see above).
The humidity sensor element is built out of a film
capacitor on different substrates. The dielectric is a
polymer which absorbs or releases water proportional
to the relative humidity of the air being drawn through
the sensor, and thus changes the capacitance of the
capacitor. For protection, the sensor element is contained
in a nylon mesh cover.
The humidity sensor and the in-vehicle temperature
sensor are connected to a Printed Circuit Board inside
the sensor housing. The PCB is powered by a 5V feed
from the ATCM. Separate signals of temperature and
relative humidity are transmitted from the PCB to the
ATCM.
SUNLIGHT SENSOR
The sunlight sensor consists of two photoelectric cells
that provide the ATCM with inputs of light intensity,
one as sensed coming from the left of the vehicle and
one as sensed coming from the right. The inputs are a
measure of the solar heating effect on vehicle occupants,
and are used by the ATCM to adjust blower speed,
temperature and distribution to improve comfort. The
sensor is installed in the center of the fascia upper
surface and is powered by a 5V feed from the ATCM.
POLLUTION SENSOR
(G421238) Technical Training48
Lesson 2 – ElectricalControl Components 
						

							The pollution sensor allows the ATCM to monitor the
ambient air for the level of hydrocarbons and oxidized
gases such as nitrous oxides, sulphur oxides and carbon
monoxide. The sensor is attached to a bracket on the
front-end carrier, at the top left corner of the condenser.
The pollution sensor is powered by a battery voltage
feed from the ATCM, and returns separate signals of
hydrocarbon and oxidized gases.
If there is a fault with the pollution sensor, the ATCM
disables the automatic operation of the recirculation
door.
SYSTEM OPERATION
A/C Compressor Control
The variable displacement A/C compressor is
permanently driven by the engine. The flow of
refrigerant through the A/C compressor, and the
resultant system pressure and evaporator operating
temperature, is regulated by the refrigerant solenoid
valve. Operation of the refrigerant solenoid valve is
controlled by the ATCM using a 400 Hz Pulse Width
Modulated (PWM) signal. The duty cycle of the PWM
signal is calculated using the following parameters:
•A/C compressor torque.
•A/C compressor torque maximum.
•A/C cooling status.
•A/C demand.
•A/C refrigerant pressure.
•Ambient air temperature.
•Blower speed.
•Engine cranking status.
•Evaporator temperature.
•Transmission gear status.
When A/C is selected, the ATCM maintains the
evaporator at an operating temperature that varies with
the in-vehicle cooling requirement. The ATCM increases
the evaporator operating temperature, by reducing the
refrigerant flow, as the requirement for air cooling
decreases, and vice versa. During an increase of
evaporator operating temperature, to avoid
compromising the dehumidification function, the ATCM
controls the rate of temperature increase, which keeps
the cabin humidity at a comfortable level.
When the economy mode is selected, the PWM signal
holds the refrigerant solenoid valve in the minimum
flow position, effectively switching off the A/C function.
The ATCM incorporates limits for the operating pressure
of the refrigerant system. When the system approaches
the high pressure limit, the duty cycle of the PWM
signal is progressively reduced until the system pressure
decreases. When the system pressure falls below the
low pressure limit, the duty cycle of the PWM signal is
held at its lowest setting, so that the A/C compressor is
maintained at the minimum stroke, to avoid depletion
of lubricant from the A/C compressor. The protection
algorithm is calculated at a high rate, to enable early
detection of the rapid pressure changes possible if a
system fault develops.
A/C Compressor Torque
The ATCM uses refrigerant pressure, evaporator
temperature and engine speed to calculate the torque
being used to drive the A/C compressor. The calculated
value is broadcast on the medium speed CAN bus for
the Engine Control Module (ECM), which uses the
calculated value for idle speed control and fueling
control. The ATCM also compares the calculated value
with a maximum A/C compressor torque value received
from the ECM over the medium speed CAN bus. If the
calculated value exceeds the maximum value, the
ATCM signals the refrigerant solenoid valve to reduce
the refrigerant flow, to reduce the torque being used to
drive the A/C compressor. By reducing the maximum
Control ComponentsLesson 2 – Electrical
49Technical Training (G421238) 
						

							A/C compressor torque value, the ECM is able to reduce
the load on the engine when it needs to maintain vehicle
performance or cooling system integrity.
Idle Speed Control
In order to maintain A/C cooling performance, the
ATCM requests an increase in engine idle speed if the
evaporator temperature starts to rise while the refrigerant
solenoid valve is already set to the maximum flow rate.
The increase in engine idle speed is requested in three
stages, using a medium speed CAN bus message to the
Engine Control Module (ECM).
The need for a change in idle speed is determined as
follows:
•If the evaporator temperature increases by 3 °C (5.4
°F), or to 6 °C (10.8 °F) above the target operating
temperature, over a 10 seconds period, the first stage
of idle speed increase is requested.
•When the first stage of idle speed increase is set, if
the evaporator temperature increases by 3 °C (5.4
°F), or increases to 12 °C (21.6 °F) above the target
operating temperature, over a 9 seconds period, the
second stage of idle speed increase is requested.
•When the second stage of idle speed increase is set,
if the evaporator temperature increases by 3 °C (5.4
°F), or increases to 15 °C (27 °F) above the target
operating temperature, over a 10 seconds period, the
third stage of idle speed increase is requested.
•When an idle speed increase is set, if the evaporator
temperature decreases by 3 °C (5.4 °F) over a 10
seconds period, the next stage down of idle speed
increase is requested.
Electrical Load Management
The ATCM manages the vehicle electrical loads to:
•Maintain the vehicle battery in a healthy state of
charge.
•Ensure adequate power is available for defrost
demisting during engine warm-up.
•Ensure adequate power is available for A/C during
extended periods with the engine at idle speed.
•To maintain system voltage within acceptable limits.
•To provide adequate power to meet customer
expectations.
Electrical load management is achieved by increasing
the engine idle speed and controlling the electrical load
of systems that do not affect the driveability or safety
of the vehicle.
During the engine warm-up period, the ATCM manages
the electrical load to make sure that the battery voltage
is maintained above a pre-determined level. The battery
voltage level that is maintained and the duration of the
start period varies with ambient air temperature and
engine coolant temperature. After the engine warm-up
period, the ATCM manages the electrical load to make
sure that the requested electrical load does not exceed
the generator output.
The duration of the engine warm-up period depends on
the ambient air temperature and the engine coolant
temperature when the ignition is switched on, as detailed
in the following table:
Engine Warm-up Times
Engine Coolant Temperature, °C (°F)Ambient Air Temper-
ature, °C (°F)>60 (>140)>30 to 86 to
10 to 50 to

						

							15151515>10 (>50)
15151515>5 to 41 to 0 to 32 to -10 to 14 to