Air Temperature Description and Operation SWB
The air temperature controls are divided into 4 primary areas:
| • | The Heating and Air Conditioning System. |
| • | Auxiliary heating and A/C system. |
HVAC Control Components
HVAC Control Module
The HVAC control module is a GMLAN device that interfaces between the operator
and the HVAC system to maintain air temperature and distribution settings. The battery
positive voltage circuit provides power that the control module uses for keep alive
memory (KAM). The instrument panel module (IPM), which is the vehicle power mode master,
provides a device on signal. The control module supports the following features:
Feature
| Availability
|
Purge
| Yes
|
Personalisation
| Yes
|
Actuator Calibration
| No
|
Air Temperature Actuators
The air temperature actuator consists of a DC drive motor, reduction gears,
printed circuit board (PCB) and a photo electric cell. The DC motors are provided
with a supply voltage of 12 Volts from the HCM. The photo interrupter counts the revolutions
of the DC motor drive shaft, these counts are then used by the HCM for reference to
the actuator position. When the ignition is cycled from OFF to ON the mode and temperature
actuators (doors) are driven to their 0% positions which for the temperature door
is full cold and the mode doors are to the closed position. The actuators are then
driven to the previous settings before the ignition was turned OFF by using the same
amount of counts recorded
Air Temperature Sensors
The air temperature sensors are 2-wire negative temperature co-efficient thermistors.
The vehicle uses the following air temperature sensors:
A signal and low reference circuit enables the sensor to operate. As the air
temperature surrounding the sensor increases, the sensor resistance decreases. The
sensor signal decreases as the resistance decreases. The sensor signal varies between
0-5 volts.
The inside temperature sensor operates within a temperature range between -40
to +90°C (+20.3 to +135.5°F). If the sensor is shorted to ground, voltage,
or an open, the system will operate using an estimated default value to allow the
system to operate. The ambient sensor operates within a temperature range between -30
to +70°C. If the HVAC control module has determined that the ambient temperature
sensor has failed, the driver information centre (DIC) display shall display - - -
- in place of the outside air temperature. If the sensor is shorted to ground, voltage,
or an open, the system will operate using an estimated default value to allow the
system to operate. If the engine coolant temperature is not more than 3°C (5.4°F)
above the sensor reading, or if the engine has not been started in 3 hours,
then the actual ambient air temperature sensor reading is displayed. Also at vehicle
speeds greater than 35 km/h (22 m.p.h.), the ambient air temperature
displayed may be allowed to increase, but only at a slow, filtered rate. The DIC displays
the ambient air temperature value that it receives from the HVAC control module through
a GMLAN message.
Sunload Sensor
The sunload sensor assembly, located centrally on the top of the instrument
panel near the windscreen is a 2-wire photo diode, effectively houses two sunlight
sensors one for the left side and one for the right side. The 2 sensors are
integrated into the sunload sensor assembly along with the ambient light sensor. Low
reference and signal circuits enable the sensor to operate. As the sunload increases,
the sensor signal decreases. The sensor operates within an intensity range between
completely dark and bright. The sensor signal varies between 0-5 volts.
The HVAC control module converts the signal to a range between 0-255 counts.
The sunload sensor provides the HVAC control module a measurement of the amount of
light shining on the vehicle. Bright or high intensity light causes the vehicle's
inside temperature to increase. The HVAC system compensates for the increased temperature
by diverting additional cool air into the vehicle. If the sensor is open or shorted,
no sunload adjustment occurs and the SERVICE VEHICLE SOON message is displayed.
Evaporator Temperature Sensor
The HVAC control module monitors the temperature of the air passing through
the evaporator by the A/C evaporator air temperature sensor. This sensor is located
on the evaporator core. The temperature is used to cycle the A/C compressor ON and
OFF to prevent the evaporator core from freezing. A thermistor inside the sensor varies
its resistance to monitor the evaporator air temperature. The HVAC control module
monitors the voltage drop across the thermistor when supplied with a 5-volt reference
signal. The HVAC control module will send a LS GMLAN message to the engine control
module (ECM) to request the A/C compressor piston stroke to minimum stroke if the
temperature drops below 2°C (37°F).
The sensor operates within a temperature range between -40 to +215°C
(-40 to +355°F). If the HVAC control module detects an open in the evaporator
temperature sensor or circuit, the GMLAN message sent to the ECM will not submit the
A/C ON request. The HVAC control module will then send a request to the infotainment
unit for display of the SERVICE A/C SYSTEM that will be displayed on the DIC. The
HVAC control module will also display A/C OFF on the module as long as the condition
is present.
A/C Refrigerant Pressure Sensor
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer.
A 5-volt reference, low reference, and signal circuits enable the sensor to operate.
The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant
pressure is low, the signal value is near 0 volts. When the A/C refrigerant
pressure is high, the signal value is near 5 volts.
The A/C refrigerant pressure sensor prevents the A/C system from operating when
a pressure exceeds a predetermined value.
If the ECM detects a failure in the A/C refrigerant pressure sensor or circuit,
the GMLAN message sent to the HVAC control module will be invalid. The HVAC control
module will then send a request to the infotainment unit for display of the SERVICE
A/C SYSTEM that will be displayed on the infotainment facia The HVAC control module
will also display A/C OFF on the module as long as the condition is present.
Heating and A/C Operation
The purpose of the heating and A/C System is to provide the following:
| • | Remove humidity from the interior of the vehicle. |
| • | Reduce windshield fogging. |
Regardless of the temperature setting, the following can effect the rate that
the HVAC system can achieve a desired temperature:
| • | Recirculation actuator setting. |
| • | Difference between inside and desired temperature. |
| • | Difference between ambient and desired temperature. |
| • | Blower motor speed setting. |
The HVAC control module commands or monitors the following actions when an air
temperature setting is selected.
| • | WARMEST POSITION--The air temperature actuator door position directs
maximum air flow through the heater core. |
| • | COLDEST POSITION--The air temperature actuator door position directs
maximum air flow around the heater core. |
| • | BETWEEN THE WARMEST AND COLDEST POSITION--The following sensors are
monitored to direct the appropriate amount of air through the heater core to achieve
the desired temperature: |
The A/C system is engaged by selecting any switch on the HVAC control module
except the A/C switch. The A/C switch will illuminate A/C OFF when the A/C switch
is selected. The control module sends a GMLAN A/C request message to the engine control
module (ECM) for A/C compressor operation. The following conditions must be met in
order for the HVAC to turn on the compressor :
| - | Evaporator Temperature more than 4°C (39°F). |
| - | Control module operating range 9-16 volts. |
| - | Engine coolant temperature (ECT) is less than 125°C (257°F) or
120°C (248°F). |
| - | Engine RPM is between 450-6,000 RPM. |
| - | A/C pressure is between 196 and 3200 kPa . |
Once engaged, the compressor will be disengaged for the following conditions:
| • | Throttle position is 100 percent. |
| • | A/C pressure is more than 3 137 kPa (455 psi) or
2 850 kPa (413 psi). |
| • | A/C pressure is less than 193 kPa (28 psi) or 200 kPa
(29 psi) . |
| • | Engine coolant temperature (ECT) is more than 125°C (257°F) or
120°C (248°F). |
| • | Engine speed is more than 5,500 RPM. |
| • | ECM detects high torque load. |
| • | ECM detects insufficient idle quality. |
| • | ECM detects a hard launch condition. |
Dual Zone Operation
Dual-zone (DZ) mode Dual-zone mode allows different temperatures to be set for
the left and right sides or to link them. When linked, the passenger’s side
temperature setting mirrors whatever the driver’s side temperature is set to.
To set a different temperature for the passenger’s side, adjust the passenger’s
temperature control. To link the passenger’s side temperature to the driver’s
side, press and hold the AUTO button for at least three seconds. Note Linking automatically
occurs if the passenger’s and driver’s sides are set to the same temperature
when the ignition is turned on.
Automatic Operation
In automatic operation, the HVAC control module will maintain the comfort level
inside of the vehicle by controlling the A/C compressor piston stroke, the blower
motor, the air temperature actuators, mode actuator and recirculation.
To place the HVAC system in automatic mode, the following is required:
| • | The blower motor switch must be in the AUTO position. |
| • | The air temperature switch must be in any other position other than full
hot or cold. |
| • | The mode switch must be in the AUTO position. |
Once the desired temperature is reached, the blower motor, mode, recirculation
and temperature actuators will automatically adjust to maintain the temperature selected.
The HVAC control module performs the following functions to maintain the desired air
temperature:
| • | Regulate blower motor speed. |
| • | Position the air temperature actuator. |
| • | Position the mode actuator. |
| • | Position the recirculation actuator. |
When the warmest position is selected in automatic operation, the blower speed
will stay on high speed and the air temperature actuators will stay in the full heat
position. When the coldest position is selected in automatic operation, the blower
will stay on high and the air temperature actuators will stay in the full cold position.
In cold temperatures, the automatic HVAC system will provide heat in the most
efficient manner. The vehicle operator can select an extreme temperature setting,
but the system will not warm the vehicle any faster. In warm temperatures, the automatic
HVAC system will also provide air conditioning in the most efficient manner. Selecting
an extremely cool temperature will not cool the vehicle any faster.
Air Temperature Description and Operation LWB
The air temperature controls are divided into 4 primary areas:
| • | The Heating and Air Conditioning System. |
| • | Auxiliary heating and A/C system. |
HVAC Control Components
HVAC Control Module
The HVAC control module is a GMLAN device that interfaces between the operator
and the HVAC system to maintain air temperature and distribution settings. The battery
positive voltage circuit provides power that the control module uses for keep alive
memory (KAM). The instrument panel module (IPM), which is the vehicle power mode master,
provides a device on signal. The control module supports the following features:
Feature
| Availability
|
Purge
| Yes
|
Personalisation
| Yes
|
Actuator Calibration
| No
|
Air Temperature Actuators
The air temperature actuator consists of a DC drive motor, reduction gears,
printed circuit board (PCB) and a photo electric cell. The DC motors are provided
with a supply voltage of 12 Volts from the HCM. The photo interrupter counts the revolutions
of the DC motor drive shaft, these counts are then used by the HCM for reference to
the actuator position. When the ignition is cycled from OFF to ON the mode and temperature
actuators (doors) are driven to their 0% positions which for the temperature door
is full cold and the mode doors are to the closed position. The actuators are then
driven to the previous settings before the ignition was turned OFF by using the same
amount of counts recorded
Air Temperature Sensors
The air temperature sensors are 2-wire negative temperature co-efficient thermistors.
The vehicle uses the following air temperature sensors:
A signal and low reference circuit enables the sensor to operate. As the air
temperature surrounding the sensor increases, the sensor resistance decreases. The
sensor signal decreases as the resistance decreases. The sensor signal varies between
0-5 volts.
The inside temperature sensor operates within a temperature range between -40
to +90°C (-40 to +194). If the sensor is shorted to ground, voltage, or
an open, the system will operate using an estimated default value to allow the system
to operate. The ambient sensor operates within a temperature range between -30
to +70°C (-22 to +158°F). If the HVAC control has determined that the
ambient temperature sensor has failed, the driver information centre (DIC) display
shall display - - - - in place of the outside air temperature. If the sensor is shorted
to ground, voltage, or an open, the system will operate using an estimated default
value to allow the system to operate. If the engine coolant temperature is not more
than 3°C (5.4°F) above the sensor reading, or if the engine has not been started
in 3 hours, then the actual ambient air temperature sensor reading is displayed.
Also at vehicle speeds greater than 35 km/h (22 m.p.h.), the ambient
air temperature displayed may be allowed to increase, but only at a slow, filtered
rate. The DIC displays the ambient air temperature value that it receives from the
HVAC control module through a GMLAN message.
Sunload Sensor
The sunload sensor is a 2-wire photo diode. The vehicle uses left and right
sunload sensors. The 2 sensors are integrated into the sunload sensor assembly
along with the ambient light sensor. Low reference and signal circuits enable the
sensor to operate. As the sunload increases, the sensor signal decreases. The sensor
operates within an intensity range between completely dark and bright. The sensor
signal varies between 0-5 volts. The HVAC control module converts the
signal to a range between 0-255 counts. The sunload sensor provides the
HVAC control module a measurement of the amount of light shining on the vehicle. Bright
or high intensity light causes the vehicle's inside temperature to increase. The HVAC
system compensates for the increased temperature by diverting additional cool air
into the vehicle. If the sensor is open or shorted, no sunload adjustment occurs and
the SERVICE VEHICLE SOON message is displayed.
Evaporator Temperature Sensor
The HVAC control module monitors the temperature of the air passing through
the evaporator by the A/C evaporator air temperature sensor. This sensor is located
on the evaporator core. The temperature is used to cycle the A/C compressor ON and
OFF to prevent the evaporator core from freezing. A thermistor inside the sensor varies
its resistance to monitor the evaporator air temperature. The HVAC control module
monitors the voltage drop across the thermistor when supplied with a 5-volt reference
signal. The HVAC control module will send a LS GMLAN message to the engine control
module (ECM) to request the A/C compressor piston stroke to minimum stroke if the
temperature drops below 2°C (37°F).
The sensor operates within a temperature range between -40 to +215°C
(-40 to +355°F). If the HVAC control module detects an open in the evaporator
temperature sensor or circuit, the class 2 message sent to the ECM will not
submit the A/C ON request. The HVAC control module will then send a request to the
infotainment unit for display of the SERVICE A/C SYSTEM that will be displayed on
the DIC. The HVAC control module will also display A/C OFF on the module as long as
the condition is present.
A/C Refrigerant Pressure Sensor
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer.
A 5-volt reference, low reference, and signal circuits enable the sensor to operate.
The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant
pressure is low, the signal value is near 0 volts. When the A/C refrigerant
pressure is high, the signal value is near 5 volts.
The A/C refrigerant pressure sensor prevents the A/C system from operating when
a pressure exceeds a predetermined value.
If the ECM detects a failure in the A/C refrigerant pressure sensor or circuit,
the class 2 message sent to the HVAC control module will be invalid. The HVAC
control module will then send a request to the infotainment unit for display of the
SERVICE A/C SYSTEM that will be displayed on the infotainment facia The HVAC control
module will also display A/C OFF on the module as long as the condition is present.
Heating and A/C Operation
The purpose of the heating and A/C System is to provide the following:
| • | Remove humidity from the interior of the vehicle. |
| • | Reduce windshield fogging. |
Regardless of the temperature setting, the following can effect the rate that
the HVAC system can achieve a desired temperature:
| • | Recirculation actuator setting. |
| • | Difference between inside and desired temperature. |
| • | Difference between ambient and desired temperature. |
| • | Blower motor speed setting. |
The HVAC control module commands or monitors the following actions when an air
temperature setting is selected.
| • | WARMEST POSITION - The air temperature actuator door position directs
maximum air flow through the heater core. |
| • | COLDEST POSITION - The air temperature actuator door position directs
maximum air flow around the heater core. |
| • | BETWEEN THE WARMEST AND COLDEST POSITION - The following sensors are monitored
to direct the appropriate amount of air through the heater core to achieve the desired
temperature: |
The A/C system is engaged by selecting any switch on the HVAC control module
except the A/C switch. The A/C switch will illuminate A/C OFF when the A/C switch
is selected. The control module sends a GMLAN A/C request message to the engine control
module (ECM) for A/C compressor operation. The following conditions must be met in
order for the HVAC to turn on the compressor :
| - | Evaporator Temperature more than 4°C (39°F). |
| - | Control module operating range 9-16 volts. |
| - | Engine coolant temperature (ECT) is less than 125°C (257°F) or
120°C (248°F). |
| - | Engine RPM is between 450-6,000 RPM. |
| - | A/C pressure is between 196 and 3200 kPa. |
Once engaged, the compressor will be disengaged for the following conditions:
| • | Throttle position is 100 percent. |
| • | A/C pressure is more than 3 137 kPa (455 psi) or
2 850 kPa (413 psi). |
| • | A/C pressure is less than 193 kPa (28 psi) or 200 kPa
(29 psi). |
| • | Engine coolant temperature (ECT) is more than 125°C (257°F) or
120°C (248°F). |
| • | Engine speed is more than 5,500 RPM. |
| • | ECM detects high torque load. |
| • | ECM detects insufficient idle quality. |
| • | ECM detects a hard launch condition. |
Dual Zone Operation
Dual-zone (DZ) mode Dual-zone mode allows different temperatures to be set for
the left and right sides or to link them. When linked, the passenger’s side
temperature setting mirrors whatever the driver’s side temperature is set to.
To set a different temperature for the passenger’s side, adjust the passenger’s
temperature control. To link the passenger’s side temperature to the driver’s
side, press and hold the AUTO button for at least three seconds. Note Linking automatically
occurs if the passenger’s and driver’s sides are set to the same temperature
when the ignition is turned on. On a tri-zone climate control 3, the rear temperature
setting mirrors whatever the driver’s side temperature is set to.
Tri Zone Operation
Selecting tri-zone (TZ) mode activates the rear passenger controls. The climate
control can still be operated as described in section Dual-zone (DZ) mode. Note The
rear passenger controls are only activated when tri-zone (TZ) is selected. Refer to
Rear passenger controls further on in this section.
Automatic Operation
In automatic operation, the HVAC control module will maintain the comfort level
inside of the vehicle by controlling the A/C compressor piston stroke, the blower
motor, the air temperature actuators, mode actuator and recirculation.
To place the HVAC system in automatic mode, the following is required:
| • | The blower motor switch must be in the AUTO position. |
| • | The air temperature switch must be in any other position other than full
hot or cold. |
| • | The mode switch must be in the AUTO position. |
Once the desired temperature is reached, the blower motor, mode, recirculation
and temperature actuators will automatically adjust to maintain the temperature selected.
The HVAC control module performs the following functions to maintain the desired air
temperature:
| • | Regulate blower motor speed. |
| • | Position the air temperature actuator. |
| • | Position the mode actuator. |
| • | Position the recirculation actuator. |
When the warmest position is selected in automatic operation, the blower speed
will stay on high speed and the air temperature actuators will stay in the full heat
position. When the coldest position is selected in automatic operation, the blower
will stay on high and the air temperature actuators will stay in the full cold position.
In cold temperatures, the automatic HVAC system will provide heat in the most
efficient manner. The vehicle operator can select an extreme temperature setting,
but the system will not warm the vehicle any faster. In warm temperatures, the automatic
HVAC system will also provide air conditioning in the most efficient manner. Selecting
an extremely cool temperature will not cool the vehicle any faster.
Auxiliary HVAC Control Module
Turn the rear temperature control L clockwise (warmer) or counterclockwise (cooler)
to set the temperature for the rear. The rear temperature setting is shown in the
front and rear displays when adjusting it. Note The rear temperature is dependent
on the driver’s side temperature. When the pointer is set to the centre of the
bar graphic in the display, the rear temperature is set to approximately the same
setting as for the driver’s side. Press + or - on the fan button to increase
or decrease the fan speed. The fan speed is shown in the display. Note This will affect
the fan speed for all three zones. Press the mode button to switch between the following
positions for the rear: Floor mode directs air to the floor-level outlets located
under the front seats. Face mode directs air to the vents in the rear of the centre
console Bi-level mode directs air to the floor-level outlets and the vents in the
rear of the centre console The setting is shown in the display. Note If windscreen
defrost is set, no air will come out of the rear vents. Pressing the AUTO button switches
the system to full automatic control. Note When pressing the AUTO button, all functions
(including the fan speed) are controlled automatically. Press the ON button P to switch
the air to the rear off or on. FAN OFF appears in the display when it is off.
Auxiliary Air Temperature Actuator
The auxiliary air temperature actuator consists of a DC drive motor, reduction
gears, printed circuit board (PCB) and a photo electric cell. The DC motors are provided
with a supply voltage of 12 Volts from the HCM. The photo interrupter counts the revolutions
of the DC motor drive shaft, these counts are then used by the HCM for reference to
the actuator position. When the ignition is cycled from OFF to ON the mode and temperature
actuators (doors) are driven to their 0% positions which for the temperature door
is full cold and the mode doors are to the closed position. The actuators are then
driven to the previous settings before the ignition was turned OFF by using the same
amount of counts recorded.
