Automatic HVAC Description and Operation LHD
HVAC Unit Construction, Components and Associated Sensors
In-Car Temperature Sensor
The in-car temperature sensor is an NTC thermistor used to monitor the vehicles's
interior temperature. Resistance signals are constantly monitored by the OCC module
and are used for subsequent control of the OCC system.
It is essential that the venturi and aspirator tube assembly by properly connected
to the in-car temperature sensor if the sensor is to provide correct information to
the OCC module.
The in-car temperature sensor (1) is located on the left-hand side of
the steering column (2) behind the sensor inlet air holes (3) on the
instrument cluster trim assembly.
Evaporator Temperature Sensor
The evaporative temperature sensor is an NTC thermistor used to monitor the
temperature of the air into the HVAC unit after it has passed through the evaporator
core. Resistance values are constantly monitored by the OCC module and are used for
subsequent control of the OCC system.
The evaporative temperature sensor (1) is located on evaporator core (2)
by a plastic retaining clip (3). The installation point of the sensor to the
evaporator is critical for correct OCC system performance.
It is an NTC thermistor used to monitor the ambient (outside) temperature. This
sensor is slow reacting due to the dense plastic housing surrounding it. The OCC takes
into account road speed before updating the temperature display to avoid false readings
in heavy traffic or extended idle conditions.
Resistance signals are sent directly from the ambient temperature sensor to
the OCC module for interpretation.
Automatic HVAC Description and Operation SWBRHD
- Mode directions UP - Defrost, Bi-Level, Blend, Face, Floor
- A/C Compressor output - OFF/output increase
- Occupant climate control ON/OFF - Sleep mode, the air mix actuators
are still operating in the back ground to try and maintain the selected set temperatures,
which means at ON (wake up) the temperature output will be near the selected set temperatures.
- Fully automatic mode - auto text is illuminated when in fully automatic
mode. auto text is off, the occupant climate control is in semi automatic mode.
- Temperature adjustment Driver Side - Set Temperature Range - Full
cold to full hot, 17 to 30 in 1 (one) degree increments.
- Mode directions Down - Floor, Face, Blend, Bi-Level, Defrost.
- Blower speeds - Semi automatic mode Twenty (20) speeds. Fully automatic
mode infinite speeds.
- Fresh / Recirculation - When in recirculation mode, will automatically
go to fresh air after Thirty (30) minutes depending on ambient temperature.
- Temperature adjustment Passenger side - Set temperature range -
Full cold to full hot, 17 to 30 in 1 (one) degree increments.
- Ambient temperature display - The ambient temperature is displayed
on the infotainment facia when the button is pressed.
- Rear window defrost - Automatically turns off after 15 minutes the
first time then every 5 minutes.
- Front windscreen defrost - In this mode the A/C is automatically
ON, Recirculation is not allowed.
General Description
The VE occupant climate control HVAC will be provided in Two (2) Variants: Dual
Zone (DZ) - Temperature adjustment is independent for both Passenger and Drivers side.
A module called the HVAC control module (HCM) is attached to the HVAC on the
Passenger side is the micro processor used to monitor inputs, process data, calculate
changes to operating functions and control HVAC outputs.
The Inputs are:
| • | Can Bus information - Priority key user, Engine RPM, Vehicle road
speed, Coolant temperature, A/C system pressure via the pressure transducer. |
| • | In-car temperature sensor. |
| • | Ambient temperature sensor. |
| • | Evaporative temperature sensor. |
| • | Electric mode actuators (DC motors) voltage, position feed back via photo
interrupters. |
| • | Variable stroke compressor electronic control valve displacement (ECVD)
actual position. |
The Outputs are:
| • | Air distribution mode - Face, Floor, Defrost, Blend, Bi-Level, Air
intake and Rear Passenger. |
| • | Vent temperatures by adjusting the air mixing doors, including the rear
passenger. |
| • | infotainment facia for display changes and Ambient temperature reading. |
| • | Rear window defrost relay. |
| • | Compressor displacement (output) via the ECVD. From OFF to Maximum output. |
| • | Variable stroke compressor ECVD (electronic control valve) target position. |
| • | Maximum blower fan speed relay. |
Recommended Settings:
The vehicle owner should be encouraged to use the occupant climate control in
fully Automatic mode and at a set temperature of between 22-24 degrees. Changing
the set temperature to suit different conditions may cause the occupant climate control
to behave differently from what the customer expects (eg. Setting to 17°C on a
hot day may cause the customer to complain that the blower fan speed is too high).
Occupant Climate Control (OCC) When OFF is Selected:
| ⇒ | The vehicle owner should be made aware that if the occupant climate control
system is turned OFF, the following will occur: |
| • | The air mixing (temperature) electric actuators will continue to operate
(motor movement noise) in the background so as to make sure that when the occupant
climate control system is re-activated it will be closer to the set temperature before
the occupant climate control system was turned OFF. |
| • | Default mode for the air inlet is fresh air, which will mean to the vehicle
owner that even though the blower fan is not operating, when driving Ram air will
forced into the HVAC. Depending on the set temperature before turning the occupant
climate control OFF the vehicle owner may feel either too Hot or too Cold. If this
is the case we suggest that they manually select Recirculation mode, this will prevent
the Ram air from entering the HVAC |
Automatic and Semi Automatic Mode - DZ and TZ:
The occupant climate control system should be set to automatic mode as in this
mode the occupant climate control system will automatically control the vehicles interior
temperature to the selected set temperature by the vehicles owner. The vehicle owner
has the option of selecting semi automatic mode to "over rule" a function
used in automatic mode. They might not like the blower fan speed selected in automatic
mode, so they have the option of adjusting the Blower fan speed by operating that
function on the infotainment facia, This will then take the occupant climate control
system into semi automatic mode. This means that the occupant climate control system
is still monitoring all the sensor readings and making automatic changes to mode and
temperature, but - it can no longer use the blower motor as part of it’s
calculations for altering the system, as the vehicle owner now has control of that
function. The occupant climate control will try and compensate for having no blower
fan speed control by altering another component to aid in meeting the required set
interior temperature
Points to Remember on DZ Occupant Climate Control (OCC) Systems:
The occupant climate control system will alter mode positions, blower fan speeds
and temperature in either automatic or semi automatic mode. These modes are face and
floor. The passenger cannot have an individual blower speed from the driver as there
is only one (1) blower motor in the HVAC.
Solar Load
The solar load sensor is located in the defrost panel of the crash pad. The
sensor body houses two solar sensors, one for the passenger side and one for the driver
side of the vehicle interior. These sensors are positioned at an approximate angle
of 40 degrees so the side windows are also covered for solar load changes. A twilight
sensor for automatic headlamp function is also contained in the solar sensor body.
Side Window Defrost Air Bleed from the HVAC - DZ :
As a design intention there is a constant bleed of air to the side windows in
face mode. This air bleed is used to keep the side windows clear of any fogging that
may be caused by the vehicle owner's breath exhaling, especially at low ambient temperatures.
There is also an air bleed to defrost in floor mode
Evaporator Temperature Control
As the A/C system uses a Denso variable stroke and "clutchless"
compressor that utilises an ECVD (electronic control valve) operated via the HVAC
Control Module to increase or decrease the crankcase pressure in the compressor, which
then alters the compressor output (displacement). The evaporator temperature sensor
has no bearing on the cycling of the compressor as there is no direct or indirect
electrical connection to the compressor from the vehicles wiring harness, as no clutch
exists on the compressor. The compressor is operating constantly when the engine is
operating, only the compressor output is adjusted. The evaporator temperature sensor
is located in the lower section of the HVAC in the air intake stream after the evaporator
and is used for sensing the incoming air temperature after the evaporator into the
HVAC, to be used as part of the output calculation by the evaporator temperature sensor
values are also required to operate the ECVD (electronic control valve) of the compressor
to alter the stroke (displacement / output) for the A/C system.
Blower Fan Control:
| • | Automatic Mode - There are stepless and varying Blower fan speeds
available. These are selected by the dependant on the input signals. |
| • | Semi Automatic Mode - There are twenty (20) blower fan speeds available
for selection by the vehicle owner. |
| ⇒ | The blower fan speeds are will vary according to: |
| • | Vehicle road speed - When the vehicle is travelling down the highway,
the ram air effect into the HVAC, in fresh air mode will increase the air force coming
from the vents, so will decrease the blower fan speed to compensate for this ram air. |
| • | In car temperature sensor. |
| • | Ambient air temperature sensor. |
| • | Solar load sensor - If the cabin temperature is at or near the set
temperature, the blower fan will be at the minimum. An increase in sun load will cause
the blower fan speed to increase. Example: Ambient temperature 30 degree, high sun
load, the blower fan will be on maximum to provide more cooling. If the vehicle enters
a tunnel, all of a sudden the sun load has dramatically reduced, causing the vehicle
owner to feel colder, The blower fan speed is reduced until the vehicle emerges from
the tunnel. |
| • | Drivers set temperature. |
| • | Air distribution mode i.e.. Fresh or Recirculation mode. |
Air Distribution Control
| ⇒ | There are six distribution air modes that can be selected, either automatically
or Semi Automatically. These are: |
| • | Blend (Floor and Defrost). |
| • | Bi-Level (Floor and Face). |
| • | Centre console rear outlet. |
When in Automatic mode and a set temperature above 25°C, only Floor and
Defrost will be selected. If the set temperature is below 25°C, Face will be selected.
If the vehicle interior temperature is at the desired temperature, the occupant climate
control will select either Bi-Level (floor/face) or Face only, dependant on if the
cabin temperature is required to warm up or cooled down. If cooling of the cabin is
required, Floor mode may be selected for a short time (A/C purge), followed by Face
mode. If heating of the cabin is required, Defrost mode will be selected until the
engine coolant temperature is warm enough, this is called Defrost delay, then followed
by Blend (floor/defrost). Then as the in car temperature increases, the mode should
change to Bi-Level (floor/face). If heating is required and the coolant temperature
is warm, Floor mode may be selected for a short time (Purge), followed by Bi-Level
(floor/face) or Blend (floor/defrost), depending on conditions.
Air Inlet Control:
When Recirculation mode is selected either automatically or manually, the occupant
climate control will return the air inlet to Fresh air mode after approximately 30
minutes, briefly and then will return to recirculation mode, this is to avoid a Carbon
Dioxide build up in the cabin through exhaling by the vehicle occupants, which will
cause drowsiness.
Automatic Mode:
| ⇒ | The air inlet mode selected will vary according to: |
| • | Drivers set temperature. |
| • | Evaporator temperature. |
| • | Engine coolant temperature. |
If the vehicle cabin does not require cooling, fresh air will be selected. If
extreme cooling of the vehicle cabin is required, such as when the ambient temperature
is high and the vehicle has been standing in direct sunlight for an extended period,
fresh may be selected for a short time (fresh delay), then recirculation mode until
the vehicle cabin has cooled down. The Fresh air the engine bay cooling temperature
becomes very high, Recirculation may be selected to increase cooling of the Vehicle
Radiator.
Vent Air Temperature Control
The vent temperatures will vary between approximately 5 degrees C (Maximum cooling)
and 70 degrees C (maximum heating). The temperature coming from the vent positions
may / will be higher or lower than what is selected by the vehicle owner as a set
temperature.
Semi Automatic Mode
This mode is where the passenger can adjust their set temperature, independent
of the driver side set temperature. To access this mode when the driver set temp is
in "locked mode", meaning that when the driver alters the set temperature,
it alters both sides. For "unlocking mode", the passenger simply adjusts
their temperature and the set temperature then becomes independent from the driver
side set temperature. If the occupant climate control was in automatic mode the AUTO
button LED illuminated, it will then go to semi automatic mode AUTO button LED not
illuminated.
Automatic Mode
| ⇒ | When a set temperature of between 17degrees C and 30 degrees C is selected,
the air temperature will be controlled automatically. The Vent temperature will vary
according to: |
| • | Driver or Passenger side set temperature. |
| ⇒ | When the vehicle cabin is at the desired temperature, the average vent air temperature
should be the same as the set temperature. If the vehicle cabin requires cooling,
the occupant climate control will try to control the vent temperature to less than
the set temperature. If the vehicle cabin requires heating, the occupant climate control
will try to control the vent temperature to be more than the set temperature. The
more cooling required, the higher the vent temperature. Generally, the Blower fan
speed will be low (less than 50%) before the occupant climate control starts to control
the temperature. (e.g. When extreme cooling is required, the blower fan will start
at maximum and the air mix will start at minimum. As the vehicle cabin temperature
cools downs, the blower speed will decrease gradually. |
| • | Increasing the set temperature will increase the vent temperature (providing
air mix is not at maximum). |
| • | Decreasing the set temperature will decrease the vent temperature (providing
air mix is not at minimum). |
| • | As the In car temperature increases, the vent temperature will decrease. |
| • | As the Solar load decreases, the vent temperature will increase. |
| • | As the Solar load increases, the vent temperature will decrease. |
| • | As the Ambient temperature increases, the vent temperature will decrease. |
| • | As the Ambient temperature decreases, the vent temperature will increase. |
Occupant Climate Control (OCC) Cold Start Routines.
| ⇒ | There are Four cold start routines incorporated into the occupant climate control
system logic to cater for various conditions on first "key on" in the
morning, typically at low ambient temperatures. |
| ⇒ | Each routine has its own respective set of criteria to satisfy before the routine
is executed: |
| • | Recirculation Delay: Automatically defaults to recirculation mode to prevent
further ingress of cold air into the vehicle cabin. |
| • | Defrost Delay: To reduce cold air at the floor during warm-up and prevents
the driver breath from "fogging up" the front windscreen. |
| • | HVAC Purge: Allows engine coolant to heat up the heater core and avoid
humidity to face and windscreen when the blower fan is activated. |
| • | A/C Purge: To avoid hot air blowing on face when the blower fan is activated. |
| • | Fresh Delay: Uses cooler outside air to purge hot air from the vehicle. |
HVAC Unit Construction, Components and Associated Sensors
General Description
There is one type of Occupant Climate Control (OCC) HVAC module assemblies fitted
across the VE Series Vehicle range:
Dual zone system-HVAC (OCC)
In-Car Temperature Sensor
The in-car temperature sensor is an negative temperature coefficient (NTC) thermistor
used to monitor the vehicles's interior temperature. Resistance signals are constantly
monitored by the OCC module and are used for subsequent control of the OCC system.
It is essential that the venturi and aspirator tube assembly by properly connected
to the in-car temperature sensor if the sensor is to provide correct information to
the OCC module.
The in-car temperature sensor is located on the left-hand side of the steering
column behind the sensor inlet air holes (1) on the instrument cluster trim
assembly.
Evaporator Temperature Sensor
The evaporative temperature sensor is a negative temperature coefficient (NTC)
thermistor used to monitor the temperature of the air into the HVAC module assembly
after it has passed through the evaporator core. Resistance values are constantly
monitored by the OCC module and are used for subsequent control of the OCC system.
The evaporative temperature sensor (1) is located on the HVAC case by
a plastic retaining clip in the down stream air flow of the evaporator.
Ambient Temperature Sensor
The ambient temperature sensor (1) is installed on a bracket (2)
that is located at the front of the A/C condenser (3), on the lower right-hand
side.
It is a negative temperature coefficient NTC thermistor used to monitor the
ambient (outside) temperature. This sensor is slow reacting, due to the dense plastic
housing surrounding it. The OCC takes into account road speed before updating the
temperature display to avoid false readings in heavy traffic or extended idle conditions.
Resistance signals are sent directly from the ambient temperature sensor to
the OCC module for interpretation.
Sun Load Sensor
The sun load sensor (1) is located in the centre of the defrost panel
to monitor the sun's heating load upon the vehicle.
It is a photochemical type sensor, where a small electrical current will be
generated, which depending on the sun load (strength) over it. When the sun's intensity
is high, the OCC module will select a higher blower fan speed and increased vehicle
cooling automatically. Likewise, when the sun load is low, such as going into an underground
car park, the OCC module will automatically reduce the fan speeds and increase heating
slightly.
Signals are sent from the sun load senor directly to the BCM, then to the OCC
module via the serial data line input.
Automatic HVAC Description and Operation LWBRHD
- Mode directions UP - Defrost, Bi-Level, Blend, Face, Floor
- A/C Compressor output - OFF/output increase
- Occupant climate control ON/OFF - Sleep mode, the air mix actuators
are still operating in the back ground to try and maintain the selected set temperatures,
which means at ON (wake up) the temperature output will be near the selected set temperatures.
- Fully automatic mode - auto text is illuminated when in fully automatic
mode. auto text is off, the occupant climate control is in semi automatic mode.
- Temperature adjustment Driver Side - Set Temperature Range - Full
cold to full hot, 17 to 30 in 1 (one) degree increments.
- Mode directions Down - Floor, Face, Blend, Bi-Level, Defrost .
- Blower speeds - Semi automatic mode Twenty (20) speeds. Fully automatic
mode infinite speeds.
- Fresh / Recirculation - When in recirculation mode, will automatically
go to fresh air after Thirty (30) minutes depending on ambient temperature.
- Zone - When the tri zone (TZ) text is ON, the rear passenger control
is activated.
- Temperature adjustment Passenger side - Set temperature range -
Full cold to full hot, 17 to 30 in 1 (one) degree increments.
- Ambient temperature display - The ambient temperature is displayed
on the infotainment facia when the button is pressed.
- Rear window defrost - Automatically turns off after 15 minutes the
first time then every 5 minutes.
- Front windscreen defrost - In this mode the A/C is automatically
ON, Recirculation is not allowed.
General Description
The WM occupant climate control HVAC will be provided in Two (2) Variants: Dual
Zone (DZ) - Temperature adjustment is independent for both Passenger and Drivers side:
Tri Zone (TZ) - Temperature adjustment is independent for both Passenger and Drivers
side and the rear Passenger through the centre console rear outlet using independent
controls
A module called the HVAC control module (HCM) is attached to the HVAC on the
Passenger side is the micro processor used to monitor inputs, process data, calculate
changes to operating functions and control HVAC outputs.
The Inputs are:
| • | Can Bus information - Priority key user, Engine RPM, Vehicle road
speed, Coolant temperature, A/C system pressure via the pressure transducer. |
| • | In-car temperature sensor. |
| • | Ambient temperature sensor. |
| • | Evaporative temperature sensor. |
| • | Electric mode actuators (DC motors) voltage, position feed back via photo
interrupters. |
| • | Customer settings by way of the infotainment facia and the head liner
HVAC controls (TZ only). |
| • | Variable stroke compressor electronic control valve displacement (ECVD)
actual position. |
The Outputs are:
| • | Air distribution mode - Face, Floor, Defrost, Blend, Bi-Level, Air
intake and Rear Passenger. |
| • | Vent temperatures by adjusting the air mixing doors, including the rear
passenger. |
| • | infotainment facia for display changes and Ambient temperature reading. |
| • | Rear window defrost relay. |
| • | Compressor displacement (output) via the ECVD. From OFF to Maximum output. |
| • | Variable stroke compressor ECVD (electronic control valve) target position. |
| • | Maximum blower fan speed relay. |
Recommended Settings:
The vehicle owner should be encouraged to use the occupant climate control in
fully Automatic mode and at a set temperature of between 22-24 degrees. Changing
the set temperature to suit different conditions may cause the occupant climate control
to behave differently from what the customer expects (eg. Setting to 17°C on a
hot day may cause the customer to complain that the blower fan speed is too high).
Occupant Climate Control (OCC) When OFF is Selected:
| ⇒ | The vehicle owner should be made aware that if the occupant climate control
system is turned OFF, the following will occur: |
| • | The air mixing (temperature) electric actuators will continue to operate
(motor movement noise) in the background so as to make sure that when the occupant
climate control system is re-activated it will be closer to the set temperature before
the occupant climate control system was turned OFF. |
| • | Default mode for the air inlet is fresh air, which will mean to the vehicle
owner that even though the blower fan is not operating, when driving Ram air will
forced into the HVAC. Depending on the set temperature before turning the occupant
climate control OFF the vehicle owner may feel either too Hot or too Cold. If this
is the case we suggest that they manually select Recirculation mode, this will prevent
the Ram air from entering the HVAC |
Automatic and Semi Automatic Mode - DZ and TZ:
The occupant climate control system should be set to automatic mode as in this
mode the occupant climate control system will automatically control the vehicles interior
temperature to the selected set temperature by the vehicles owner. The vehicle owner
has the option of selecting semi automatic mode to "over rule" a function
used in automatic mode. They might not like the blower fan speed selected in automatic
mode, so they have the option of adjusting the Blower fan speed by operating that
function on the infotainment facia, This will then take the occupant climate control
system into semi automatic mode. This means that the occupant climate control system
is still monitoring all the sensor readings and making automatic changes to mode and
temperature, but - it can no longer use the blower motor as part of it’s
calculations for altering the system, as the vehicle owner now has control of that
function. The occupant climate control will try and compensate for having no blower
fan speed control by altering another component to aid in meeting the required set
interior temperature
Points to Remember on DZ and TZ Occupant Climate Control (OCC) Systems:
The occupant climate control system will alter mode positions, blower fan speeds
and temperature in either automatic or semi automatic mode. These modes are face and
floor. The passenger cannot have an individual blower speed from the driver as there
is only one (1) blower motor in the HVAC.
Solar Load
The solar load sensor is located in the defrost panel of the crash pad. The
sensor body houses two solar sensors, one for the passenger side and one for the driver
side of the vehicle interior. These sensors are positioned at an approximate angle
of 40 degrees so the side windows are also covered for solar load changes. A twilight
sensor for automatic headlamp function is also contained in the solar sensor body.
Side Window Defrost Air Bleed from the HVAC - DZ and TZ:
As a design intention there is a constant bleed of air to the side windows in
face mode. This air bleed is used to keep the side windows clear of any fogging that
may be caused by the vehicle owner's breath exhaling, especially at low ambient temperatures.
There is also an air bleed to defrost in floor mode
Evaporator Temperature Control
As the A/C system uses a Denso variable stroke and "clutchless"
compressor that utilises an ECVD (electronic control valve) operated via the HVAC
Control Module to increase or decrease the crankcase pressure in the compressor, which
then alters the compressor output (displacement). The evaporator temperature sensor
has no bearing on the cycling of the compressor as there is no direct or indirect
electrical connection to the compressor from the vehicles wiring harness, as no clutch
exists on the compressor. The compressor is operating constantly when the engine is
operating, only the compressor output is adjusted. The evaporator temperature sensor
is located in the lower section of the HVAC in the air intake stream after the evaporator
and is used for sensing the incoming air temperature after the evaporator into the
HVAC, to be used as part of the output calculation by the . The evaporator temperature
sensor values are also required to operate the ECVD (electronic control valve) of
the compressor to alter the stroke (displacement / output) for the A/C system.
Blower Fan Control:
| • | Automatic Mode - There are step less and varying Blower fan speeds
available. These are selected by the dependant on the input signals. |
| • | Semi Automatic Mode - There are twenty (20) blower fan speeds available
for selection by the vehicle owner. |
| ⇒ | The blower fan speeds are will vary according to: |
| • | Vehicle road speed - When the vehicle is travelling down the highway,
the ram air effect into the HVAC, in fresh air mode will increase the air force coming
from the vents, so will decrease the blower fan speed to compensate for this ram air. |
| • | In car temperature sensor. |
| • | Ambient air temperature sensor. |
| • | Solar load sensor - If the cabin temperature is at or near the set
temperature, the blower fan will be at the minimum. An increase in sun load will cause
the blower fan speed to increase. Example: Ambient temperature 30 degree, high sun
load, the blower fan will be on maximum to provide more cooling. If the vehicle enters
a tunnel, all of a sudden the sun load has dramatically reduced, causing the vehicle
owner to feel colder, The blower fan speed is reduced until the vehicle emerges from
the tunnel. |
| • | Drivers set temperature. |
| • | Air distribution mode i.e.. Fresh or Recirculation mode. |
Air Distribution Control
| ⇒ | There are six distribution air modes that can be selected, either automatically
or Semi Automatically. These are: |
| • | Blend (floor and Defrost). |
| • | Bi-Level (Floor and Face). |
| • | Centre console rear outlet. |
When in Automatic mode and a set temperature above 25°C, only Floor and
Defrost will be selected. If the set temperature is below 25°C, Face will be selected.
If the vehicle interior temperature is at the desired temperature, the occupant climate
control will select either Bi-Level (floor/face) or Face only, dependant on if the
cabin temperature is required to warm up or cooled down. If cooling of the cabin is
required, Floor mode may be selected for a short time (A/C purge), followed by Face
mode. If heating of the cabin is required, Defrost mode will be selected until the
engine coolant temperature is warm enough, this is called Defrost delay, then followed
by Blend (floor/defrost). Then as the in car temperature increases, the mode should
change to Bi-Level (floor/face). If heating is required and the coolant temperature
is warm, Floor mode may be selected for a short time (Purge), followed by Bi-Level
(floor/face) or Blend (floor/defrost), depending on conditions.
Air Inlet Control:
When Recirculation mode is selected either automatically or manually, the occupant
climate control will return the air inlet to Fresh air mode after approximately 30
minutes, briefly and then will return to recirculation mode, this is to avoid a Carbon
Dioxide build up in the cabin through exhaling by the vehicle occupants, which will
cause drowsiness.
Automatic Mode:
| ⇒ | The air inlet mode selected will vary according to: |
| • | Drivers set temperature. |
| • | Evaporator temperature. |
| • | Engine coolant temperature. |
If the vehicle cabin does not require cooling, fresh air will be selected. If
extreme cooling of the vehicle cabin is required, such as when the ambient temperature
is high and the vehicle has been standing in direct sunlight for an extended period,
fresh may be selected for a short time (fresh delay), then recirculation mode until
the vehicle cabin has cooled down. The Fresh air the engine bay cooling temperature
becomes very high, Recirculation may be selected to increase cooling of the Vehicle
Radiator.
Vent Air Temperature Control
The vent temperatures will vary between approximately 5 degrees C (Maximum cooling)
and 70 degrees C (maximum heating). The temperature coming from the vent positions
may / will be higher or lower than what is selected by the vehicle owner as a set
temperature.
Semi Automatic Mode
This mode is where the passenger can adjust their set temperature, independent
of the driver side set temperature. To access this mode when the driver set temp is
in "locked mode", meaning that when the driver alters the set temperature,
it alters both sides. For "unlocking mode", the passenger simply adjusts
their temperature and the set temperature then becomes independent from the driver
side set temperature. If the occupant climate control was in automatic mode the AUTO
button LED illuminated, it will then go to semi automatic mode AUTO button LED not
illuminated.
Automatic Mode
| ⇒ | When a set temperature of between 17degrees C and 30 degrees C is selected,
the air temperature will be controlled automatically. The Vent temperature will vary
according to: |
| • | Driver or Passenger side set temperature. |
| ⇒ | When the vehicle cabin is at the desired temperature, the average vent air temperature
should be the same as the set temperature. If the vehicle cabin requires cooling,
the occupant climate control will try to control the vent temperature to less than
the set temperature. If the vehicle cabin requires heating, the occupant climate control
will try to control the vent temperature to be more than the set temperature. The
more cooling required, the higher the vent temperature. Generally, the Blower fan
speed will be low (less than 50%) before the occupant climate control starts to control
the temperature. (e.g. When extreme cooling is required, the blower fan will start
at maximum and the air mix will start at minimum. As the vehicle cabin temperature
cools downs, the blower speed will decrease gradually. |
| • | Increasing the set temperature will increase the vent temperature (providing
air mix is not at maximum). |
| • | Decreasing the set temperature will decrease the vent temperature (providing
air mix is not at minimum). |
| • | As the In car temperature increases, the vent temperature will decrease. |
| • | As the Solar load decreases, the vent temperature will increase. |
| • | As the Solar load increases, the vent temperature will decrease. |
| • | As the Ambient temperature increases, the vent temperature will decrease. |
| • | As the Ambient temperature decreases, the vent temperature will increase. |
Occupant Climate Control (OCC) Cold Start Routines.
| ⇒ | There are Four cold start routines incorporated into the occupant climate control
system logic to cater for various conditions on first "key on" in the
morning, typically at low ambient temperatures. |
| ⇒ | Each routine has its own respective set of criteria to satisfy before the routine
is executed: |
| • | Recirculation Delay: Automatically defaults to recirculation mode to prevent
further ingress of cold air into the vehicle cabin. |
| • | Defrost Delay: To reduce cold air at the floor during warm-up and prevents
the driver breath from "fogging up" the front windscreen. |
| • | HVAC Purge: Allows engine coolant to heat up the heater core and avoid
humidity to face and windscreen when the blower fan is activated. |
| • | A/C Purge: To avoid hot air blowing on face when the blower fan is activated. |
| • | Fresh Delay: Uses cooler outside air to purge hot air from the vehicle. |
HVAC Unit Construction, Components and Associated Sensors
General Description
There are two different types of Occupant Climate Control (OCC) HVAC module
assemblies fitted across the WM Series Vehicle range:
| • | Dual zone system-HVAC (OCC) |
| • | Tri zone system-HVAC (OCC) |
Tri zone HVAC module assemblies differ from the dual zone units in that it allows
the back seat passengers to select their own temperature.
Aspirator Tube
The aspirator tube is located on the side of the HVAC case. The front section
of the tube is retained to the case by a locating lug, which locks into the HVAC case.
One retaining clip moulded to the case, retains the centre section of the tube. The
rear of the tube is fitted into the induction port of the venturi. The vase of the
venturi (inlet port) is installed to the venturi air hole, located in the evaporator
cover of the HVAC case.
In-Car Temperature Sensor
The in-car temperature sensor is an negative temperature coefficient (NTC) thermistor
used to monitor the vehicles's interior temperature. Resistance signals are constantly
monitored by the OCC module and are used for subsequent control of the OCC system.
It is essential that the venturi and aspirator tube assembly by properly connected
to the in-car temperature sensor if the sensor is to provide correct information to
the OCC module.
The in-car temperature sensor is located on the left-hand side of the steering
column behind the sensor inlet air holes (1) on the instrument cluster trim
assembly.
Evaporator Temperature Sensor
The evaporative temperature sensor is a negative temperature coefficient (NTC)
thermistor used to monitor the temperature of the air into the HVAC module assembly
after it has passed through the evaporator core. Resistance values are constantly
monitored by the OCC module and are used for subsequent control of the OCC system.
The evaporative temperature sensor (1) is located on the HVAC case by
a plastic retaining clip in the down stream air flow of the evaporator.
Ambient Temperature Sensor
The ambient temperature sensor (1) is installed on a bracket (2)
that is located at the front of the A/C condenser (3), on the lower right-hand
side.
It is a negative temperature coefficient NTC thermistor used to monitor the
ambient (outside) temperature. This sensor is slow reacting, due to the dense plastic
housing surrounding it. The OCC takes into account road speed before updating the
temperature display to avoid false readings in heavy traffic or extended idle conditions.
Resistance signals are sent directly from the ambient temperature sensor to
the OCC module for interpretation.
Sun Load Sensor
The sun load sensor (1) is located in the centre of the defrost panel
to monitor the sun's heating load upon the vehicle.
It is a photochemical type sensor, where a small electrical current will be
generated, which depending on the sun load (strength) over it. When the sun's intensity
is high, the OCC module will select a higher blower fan speed and increased vehicle
cooling automatically. Likewise, when the sun load is low, such as going into an underground
car park, the OCC module will automatically reduce the fan speeds and increase heating
slightly.
Signals are sent from the sun load senor directly to the BCM, then to the OCC
module via the serial data line input.
